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Re: [Electronics_101] Re: What kind of Temperature Sensor is this ??

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  • Donald H Locker
    The current is converted to a voltage by the 10k load resistor (E=IR). Feeding that voltage to a non-inverting input of an op amp assures that the op-amp load
    Message 1 of 18 , Jul 1, 2013
      The current is converted to a voltage by the 10k load resistor (E=IR). Feeding that voltage to a non-inverting input of an op amp assures that the op-amp load does not affect the voltage. (The other alternative would to be to have the non-sensor end of the 10k resistor connected to a "virtual" ground at the inverting input of the op amp, and have the output go [more] negative as the input goes more positive. This sort of signal is not as easy for an A/D or requires another stage to invert again to a positive voltage.)

      No need for a microammeter; measuring the voltage across the 10k resistor is adequate, as you have done. That is exactly the kind of result I would expect for a current-output temperature sensor. A thermistor would be more non-linear over that range and a thermocouple's output is a millivolt-level that would not even show up on your measurements.

      Donald.
      --
      *Plain Text* email -- it's an accessibility issue
      () no proprietary attachments; no html mail
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      ----- Original Message -----
      > From: jsternmd@...
      > To: "Electronics 101" <Electronics_101@yahoogroups.com>
      > Sent: Sunday, June 30, 2013 9:55:45 PM
      > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
      >
      > Hi Donald, Stefan,
      >
      > I will try the series resistor experiment. I don't have a microammeter
      > but its something I have wanted to add to my workbench. The AD950 or
      > other current device would be high impedance and limit changes in
      > current output with changes in supply voltage. Would you expect the
      > mVDC per degree change I observed at the sensor output lead with a
      > current device?
      >
      > Also, would a current device make sense with the way this sensor is
      > wired to the non-inverting input of the opamp? I am not too
      > experienced with opamps but I thought for a current to voltage opamp
      > the input had to go to the inverting input to get a positive voltage
      > output? The opamp output goes directly to an A-D input on a PIC-type
      > uprocessor so I assume its a voltage to digital conversion.
      >
      > Many thanks again for your advice.
      >
      > jerry
      >
      > --- In Electronics_101@yahoogroups.com, Stefan Trethan
      > <stefan_trethan@...> wrote:
      > >
      > > Making two measurements, say one with a 10k and one with a 20k
      > > resistor in series would determine if it is a current out device or
      > > a
      > > zener.
      > >
      > >
      > > ST
      > >
      > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@...>
      > > wrote:
      > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
      > > > is one possibility. There are other current-output temperature
      > > > sensors like this, though most I've seen are in larger packages.
      > > >
      > > > HTH,
      > > > Donald.
      > > > --
      > >
      >
      >
      >
      >
      > ------------------------------------
      >
      > Please trim excess when replyingYahoo! Groups Links
      >
      >
      >
    • jsternmd@att.net
      Hi Donald, Let me ask a basic question. The output of the opamp shows increasing positive voltage with increasing temperature. The sensor input is to pin 3 of
      Message 2 of 18 , Jul 1, 2013
        Hi Donald,

        Let me ask a basic question. The output of the opamp shows increasing positive voltage with increasing temperature. The sensor input is to pin 3 of the opamp which is noninverting. Wouldn't an increasing positive current input lead to a inversely decreasing output voltage relationship? Do any of the current sensors have a negative temp relationship?

        thanks
        Jerry

        --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:
        >
        > The current is converted to a voltage by the 10k load resistor (E=IR). Feeding that voltage to a non-inverting input of an op amp assures that the op-amp load does not affect the voltage. (The other alternative would to be to have the non-sensor end of the 10k resistor connected to a "virtual" ground at the inverting input of the op amp, and have the output go [more] negative as the input goes more positive. This sort of signal is not as easy for an A/D or requires another stage to invert again to a positive voltage.)
        >
        > No need for a microammeter; measuring the voltage across the 10k resistor is adequate, as you have done. That is exactly the kind of result I would expect for a current-output temperature sensor. A thermistor would be more non-linear over that range and a thermocouple's output is a millivolt-level that would not even show up on your measurements.
        >
        > Donald.
        > --
        > *Plain Text* email -- it's an accessibility issue
        > () no proprietary attachments; no html mail
        > /\ ascii ribbon campaign - <www.asciiribbon.org>
        >
        > ----- Original Message -----
        > > From: jsternmd@...
        > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
        > > Sent: Sunday, June 30, 2013 9:55:45 PM
        > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
        > >
        > > Hi Donald, Stefan,
        > >
        > > I will try the series resistor experiment. I don't have a microammeter
        > > but its something I have wanted to add to my workbench. The AD950 or
        > > other current device would be high impedance and limit changes in
        > > current output with changes in supply voltage. Would you expect the
        > > mVDC per degree change I observed at the sensor output lead with a
        > > current device?
        > >
        > > Also, would a current device make sense with the way this sensor is
        > > wired to the non-inverting input of the opamp? I am not too
        > > experienced with opamps but I thought for a current to voltage opamp
        > > the input had to go to the inverting input to get a positive voltage
        > > output? The opamp output goes directly to an A-D input on a PIC-type
        > > uprocessor so I assume its a voltage to digital conversion.
        > >
        > > Many thanks again for your advice.
        > >
        > > jerry
        > >
        > > --- In Electronics_101@yahoogroups.com, Stefan Trethan
        > > <stefan_trethan@> wrote:
        > > >
        > > > Making two measurements, say one with a 10k and one with a 20k
        > > > resistor in series would determine if it is a current out device or
        > > > a
        > > > zener.
        > > >
        > > >
        > > > ST
        > > >
        > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@>
        > > > wrote:
        > > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
        > > > > is one possibility. There are other current-output temperature
        > > > > sensors like this, though most I've seen are in larger packages.
        > > > >
        > > > > HTH,
        > > > > Donald.
        > > > > --
        > > >
        > >
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > > Please trim excess when replyingYahoo! Groups Links
        > >
        > >
        > >
        >
      • Donald H Locker
        Increasing positive current through the sensor increases the voltage across the 10k resistor. This is the same voltage that you would read across the resistor
        Message 3 of 18 , Jul 1, 2013
          Increasing positive current through the sensor increases the voltage across the 10k resistor. This is the same voltage that you would read across the resistor with a voltmeter.

          This increasing voltage applied to the non-inverting input of the op amp causes the output voltage of the op amp to increase (because vout = G(vnoninv - vinv) where G is a pretty large number - on the order of thousands to tens of thousands). The output of the op amp is connected to its inverting input (assuming a unity gain configuration) and must rise sufficiently to bring the inverting input up to the same voltage as the non-inverting input. The result is that the output voltage is [very nearly] the same voltage as the noninverting input which is the same as the inverting input (which is connected to the output) even though the output and inverting inputs are not connected to the sensor or the 10k resistor and draw no current from them.

          The current from the sensor does not go into the op amp, only through the resistor to ground (to a pretty good approximation.)

          Donald.
          --
          *Plain Text* email -- it's an accessibility issue
          () no proprietary attachments; no html mail
          /\ ascii ribbon campaign - <www.asciiribbon.org>

          ----- Original Message -----
          > From: jsternmd@...
          > To: "Electronics 101" <Electronics_101@yahoogroups.com>
          > Sent: Monday, July 1, 2013 9:45:06 PM
          > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
          > Hi Donald,
          >
          > Let me ask a basic question. The output of the opamp shows increasing
          > positive voltage with increasing temperature. The sensor input is to
          > pin 3 of the opamp which is noninverting. Wouldn't an increasing
          > positive current input lead to a inversely decreasing output voltage
          > relationship? Do any of the current sensors have a negative temp
          > relationship?
          >
          > thanks
          > Jerry
          >
          > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...>
          > wrote:
          > >
          > > The current is converted to a voltage by the 10k load resistor
          > > (E=IR). Feeding that voltage to a non-inverting input of an op amp
          > > assures that the op-amp load does not affect the voltage. (The other
          > > alternative would to be to have the non-sensor end of the 10k
          > > resistor connected to a "virtual" ground at the inverting input of
          > > the op amp, and have the output go [more] negative as the input goes
          > > more positive. This sort of signal is not as easy for an A/D or
          > > requires another stage to invert again to a positive voltage.)
          > >
          > > No need for a microammeter; measuring the voltage across the 10k
          > > resistor is adequate, as you have done. That is exactly the kind of
          > > result I would expect for a current-output temperature sensor. A
          > > thermistor would be more non-linear over that range and a
          > > thermocouple's output is a millivolt-level that would not even show
          > > up on your measurements.
          > >
          > > Donald.
          > > --
          > > *Plain Text* email -- it's an accessibility issue
          > > () no proprietary attachments; no html mail
          > > /\ ascii ribbon campaign - <www.asciiribbon.org>
          > >
          > > ----- Original Message -----
          > > > From: jsternmd@...
          > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
          > > > Sent: Sunday, June 30, 2013 9:55:45 PM
          > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
          > > > this ??
          > > >
          > > > Hi Donald, Stefan,
          > > >
          > > > I will try the series resistor experiment. I don't have a
          > > > microammeter
          > > > but its something I have wanted to add to my workbench. The AD950
          > > > or
          > > > other current device would be high impedance and limit changes in
          > > > current output with changes in supply voltage. Would you expect
          > > > the
          > > > mVDC per degree change I observed at the sensor output lead with a
          > > > current device?
          > > >
          > > > Also, would a current device make sense with the way this sensor
          > > > is
          > > > wired to the non-inverting input of the opamp? I am not too
          > > > experienced with opamps but I thought for a current to voltage
          > > > opamp
          > > > the input had to go to the inverting input to get a positive
          > > > voltage
          > > > output? The opamp output goes directly to an A-D input on a
          > > > PIC-type
          > > > uprocessor so I assume its a voltage to digital conversion.
          > > >
          > > > Many thanks again for your advice.
          > > >
          > > > jerry
          > > >
          > > > --- In Electronics_101@yahoogroups.com, Stefan Trethan
          > > > <stefan_trethan@> wrote:
          > > > >
          > > > > Making two measurements, say one with a 10k and one with a 20k
          > > > > resistor in series would determine if it is a current out device
          > > > > or
          > > > > a
          > > > > zener.
          > > > >
          > > > >
          > > > > ST
          > > > >
          > > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@>
          > > > > wrote:
          > > > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
          > > > > > is one possibility. There are other current-output temperature
          > > > > > sensors like this, though most I've seen are in larger
          > > > > > packages.
          > > > > >
          > > > > > HTH,
          > > > > > Donald.
          > > > > > --
          > > > >
          > > >
          > > >
          > > >
          > > >
          > > > ------------------------------------
          > > >
          > > > Please trim excess when replyingYahoo! Groups Links
          > > >
          > > >
          > > >
          > >
          >
          >
          >
          >
          > ------------------------------------
          >
          > Please trim excess when replyingYahoo! Groups Links
          >
          >
          >
        • jsternmd@att.net
          HI Donald, I mapped out the schematic and uploaded it to the file section: named Temperature Sensor Schematic . Does this match your thinking? thanks jerry
          Message 4 of 18 , Jul 1, 2013
            HI Donald,

            I mapped out the schematic and uploaded it to the file section: named "Temperature Sensor Schematic". Does this match your thinking?

            thanks
            jerry

            --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:
            >
            > Increasing positive current through the sensor increases the voltage across the 10k resistor. This is the same voltage that you would read across the resistor with a voltmeter.
            >
            > This increasing voltage applied to the non-inverting input of the op amp causes the output voltage of the op amp to increase (because vout = G(vnoninv - vinv) where G is a pretty large number - on the order of thousands to tens of thousands). The output of the op amp is connected to its inverting input (assuming a unity gain configuration) and must rise sufficiently to bring the inverting input up to the same voltage as the non-inverting input. The result is that the output voltage is [very nearly] the same voltage as the noninverting input which is the same as the inverting input (which is connected to the output) even though the output and inverting inputs are not connected to the sensor or the 10k resistor and draw no current from them.
            >
            > The current from the sensor does not go into the op amp, only through the resistor to ground (to a pretty good approximation.)
            >
            > Donald.
            > --
            > *Plain Text* email -- it's an accessibility issue
            > () no proprietary attachments; no html mail
            > /\ ascii ribbon campaign - <www.asciiribbon.org>
            >
            > ----- Original Message -----
            > > From: jsternmd@...
            > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
            > > Sent: Monday, July 1, 2013 9:45:06 PM
            > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
            > > Hi Donald,
            > >
            > > Let me ask a basic question. The output of the opamp shows increasing
            > > positive voltage with increasing temperature. The sensor input is to
            > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
            > > positive current input lead to a inversely decreasing output voltage
            > > relationship? Do any of the current sensors have a negative temp
            > > relationship?
            > >
            > > thanks
            > > Jerry
            > >
            > > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@>
            > > wrote:
            > > >
            > > > The current is converted to a voltage by the 10k load resistor
            > > > (E=IR). Feeding that voltage to a non-inverting input of an op amp
            > > > assures that the op-amp load does not affect the voltage. (The other
            > > > alternative would to be to have the non-sensor end of the 10k
            > > > resistor connected to a "virtual" ground at the inverting input of
            > > > the op amp, and have the output go [more] negative as the input goes
            > > > more positive. This sort of signal is not as easy for an A/D or
            > > > requires another stage to invert again to a positive voltage.)
            > > >
            > > > No need for a microammeter; measuring the voltage across the 10k
            > > > resistor is adequate, as you have done. That is exactly the kind of
            > > > result I would expect for a current-output temperature sensor. A
            > > > thermistor would be more non-linear over that range and a
            > > > thermocouple's output is a millivolt-level that would not even show
            > > > up on your measurements.
            > > >
            > > > Donald.
            > > > --
            > > > *Plain Text* email -- it's an accessibility issue
            > > > () no proprietary attachments; no html mail
            > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
            > > >
            > > > ----- Original Message -----
            > > > > From: jsternmd@
            > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
            > > > > Sent: Sunday, June 30, 2013 9:55:45 PM
            > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
            > > > > this ??
            > > > >
            > > > > Hi Donald, Stefan,
            > > > >
            > > > > I will try the series resistor experiment. I don't have a
            > > > > microammeter
            > > > > but its something I have wanted to add to my workbench. The AD950
            > > > > or
            > > > > other current device would be high impedance and limit changes in
            > > > > current output with changes in supply voltage. Would you expect
            > > > > the
            > > > > mVDC per degree change I observed at the sensor output lead with a
            > > > > current device?
            > > > >
            > > > > Also, would a current device make sense with the way this sensor
            > > > > is
            > > > > wired to the non-inverting input of the opamp? I am not too
            > > > > experienced with opamps but I thought for a current to voltage
            > > > > opamp
            > > > > the input had to go to the inverting input to get a positive
            > > > > voltage
            > > > > output? The opamp output goes directly to an A-D input on a
            > > > > PIC-type
            > > > > uprocessor so I assume its a voltage to digital conversion.
            > > > >
            > > > > Many thanks again for your advice.
            > > > >
            > > > > jerry
            > > > >
            > > > > --- In Electronics_101@yahoogroups.com, Stefan Trethan
            > > > > <stefan_trethan@> wrote:
            > > > > >
            > > > > > Making two measurements, say one with a 10k and one with a 20k
            > > > > > resistor in series would determine if it is a current out device
            > > > > > or
            > > > > > a
            > > > > > zener.
            > > > > >
            > > > > >
            > > > > > ST
            > > > > >
            > > > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@>
            > > > > > wrote:
            > > > > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
            > > > > > > is one possibility. There are other current-output temperature
            > > > > > > sensors like this, though most I've seen are in larger
            > > > > > > packages.
            > > > > > >
            > > > > > > HTH,
            > > > > > > Donald.
            > > > > > > --
            > > > > >
            > > > >
            > > > >
            > > > >
            > > > >
            > > > > ------------------------------------
            > > > >
            > > > > Please trim excess when replyingYahoo! Groups Links
            > > > >
            > > > >
            > > > >
            > > >
            > >
            > >
            > >
            > >
            > > ------------------------------------
            > >
            > > Please trim excess when replyingYahoo! Groups Links
            > >
            > >
            > >
            >
          • Donald H Locker
            Hello, Jerry. will show little or no change in voltages with changing temperature. The
            Message 5 of 18 , Jul 2, 2013
              Hello, Jerry.

              <http://groups.yahoo.com/group/Electronics_101/files/Temp%20Sensor.pdf> will show little or no change in voltages with changing temperature. The noninverting input will always be at a high voltage (somewhere between +5 and +12) and the opamp output will be high all the time.

              See the image (jpg) at <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1.jpg> for a circuit that will reproduces the 270mV at 4C, 290mV at 23C, and 350mV at 84C values reported. (Those values will appear at the NonInv node in this schematic.)

              Donald.
              --
              *Plain Text* email -- it's an accessibility issue
              () no proprietary attachments; no html mail
              /\ ascii ribbon campaign - <www.asciiribbon.org>

              ----- Original Message -----
              > From: jsternmd@...
              > To: "Electronics 101" <Electronics_101@yahoogroups.com>
              > Sent: Monday, July 1, 2013 10:34:40 PM
              > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
              > HI Donald,
              >
              > I mapped out the schematic and uploaded it to the file section: named
              > "Temperature Sensor Schematic". Does this match your thinking?
              >
              > thanks
              > jerry
              >
              > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...>
              > wrote:
              > >
              > > Increasing positive current through the sensor increases the voltage
              > > across the 10k resistor. This is the same voltage that you would
              > > read across the resistor with a voltmeter.
              > >
              > > This increasing voltage applied to the non-inverting input of the op
              > > amp causes the output voltage of the op amp to increase (because
              > > vout = G(vnoninv - vinv) where G is a pretty large number - on the
              > > order of thousands to tens of thousands). The output of the op amp
              > > is connected to its inverting input (assuming a unity gain
              > > configuration) and must rise sufficiently to bring the inverting
              > > input up to the same voltage as the non-inverting input. The result
              > > is that the output voltage is [very nearly] the same voltage as the
              > > noninverting input which is the same as the inverting input (which
              > > is connected to the output) even though the output and inverting
              > > inputs are not connected to the sensor or the 10k resistor and draw
              > > no current from them.
              > >
              > > The current from the sensor does not go into the op amp, only
              > > through the resistor to ground (to a pretty good approximation.)
              > >
              > > Donald.
              > > --
              > > *Plain Text* email -- it's an accessibility issue
              > > () no proprietary attachments; no html mail
              > > /\ ascii ribbon campaign - <www.asciiribbon.org>
              > >
              > > ----- Original Message -----
              > > > From: jsternmd@...
              > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
              > > > Sent: Monday, July 1, 2013 9:45:06 PM
              > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
              > > > this ??
              > > > Hi Donald,
              > > >
              > > > Let me ask a basic question. The output of the opamp shows
              > > > increasing
              > > > positive voltage with increasing temperature. The sensor input is
              > > > to
              > > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
              > > > positive current input lead to a inversely decreasing output
              > > > voltage
              > > > relationship? Do any of the current sensors have a negative temp
              > > > relationship?
              > > >
              > > > thanks
              > > > Jerry
              > > >

              [snip]
            • Donald H Locker
              That image uses a different op amp but the results won t really change. There is also an LTspice circuit from which the jpg was snapped at
              Message 6 of 18 , Jul 2, 2013
                That image uses a different op amp but the results won't really change. There is also an LTspice circuit from which the jpg was snapped at <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1_LTspice.zip> if you'd like to try it yourself.

                Donald.
                --
                *Plain Text* email -- it's an accessibility issue
                () no proprietary attachments; no html mail
                /\ ascii ribbon campaign - <www.asciiribbon.org>

                ----- Original Message -----
                > From: "Donald H Locker" <dhlocker@...>
                > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                > Sent: Tuesday, July 2, 2013 8:13:11 AM
                > Subject: Re: [Electronics_101] Re: What kind of Temperature Sensor is this ??
                > Hello, Jerry.
                >
                > <http://groups.yahoo.com/group/Electronics_101/files/Temp%20Sensor.pdf>
                > will show little or no change in voltages with changing temperature.
                > The noninverting input will always be at a high voltage (somewhere
                > between +5 and +12) and the opamp output will be high all the time.
                >
                > See the image (jpg) at
                > <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1.jpg>
                > for a circuit that will reproduces the 270mV at 4C, 290mV at 23C, and
                > 350mV at 84C values reported. (Those values will appear at the NonInv
                > node in this schematic.)
                >
                > Donald.
                > --
                > *Plain Text* email -- it's an accessibility issue
                > () no proprietary attachments; no html mail
                > /\ ascii ribbon campaign - <www.asciiribbon.org>
                >
                > ----- Original Message -----
                > > From: jsternmd@...
                > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                > > Sent: Monday, July 1, 2013 10:34:40 PM
                > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                > > this ??
                > > HI Donald,
                > >
                > > I mapped out the schematic and uploaded it to the file section:
                > > named
                > > "Temperature Sensor Schematic". Does this match your thinking?
                > >
                > > thanks
                > > jerry
                > >
                > > --- In Electronics_101@yahoogroups.com, Donald H Locker
                > > <dhlocker@...>
                > > wrote:
                > > >
                > > > Increasing positive current through the sensor increases the
                > > > voltage
                > > > across the 10k resistor. This is the same voltage that you would
                > > > read across the resistor with a voltmeter.
                > > >
                > > > This increasing voltage applied to the non-inverting input of the
                > > > op
                > > > amp causes the output voltage of the op amp to increase (because
                > > > vout = G(vnoninv - vinv) where G is a pretty large number - on the
                > > > order of thousands to tens of thousands). The output of the op amp
                > > > is connected to its inverting input (assuming a unity gain
                > > > configuration) and must rise sufficiently to bring the inverting
                > > > input up to the same voltage as the non-inverting input. The
                > > > result
                > > > is that the output voltage is [very nearly] the same voltage as
                > > > the
                > > > noninverting input which is the same as the inverting input (which
                > > > is connected to the output) even though the output and inverting
                > > > inputs are not connected to the sensor or the 10k resistor and
                > > > draw
                > > > no current from them.
                > > >
                > > > The current from the sensor does not go into the op amp, only
                > > > through the resistor to ground (to a pretty good approximation.)
                > > >
                > > > Donald.
                > > > --
                > > > *Plain Text* email -- it's an accessibility issue
                > > > () no proprietary attachments; no html mail
                > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                > > >
                > > > ----- Original Message -----
                > > > > From: jsternmd@...
                > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                > > > > Sent: Monday, July 1, 2013 9:45:06 PM
                > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor
                > > > > is
                > > > > this ??
                > > > > Hi Donald,
                > > > >
                > > > > Let me ask a basic question. The output of the opamp shows
                > > > > increasing
                > > > > positive voltage with increasing temperature. The sensor input
                > > > > is
                > > > > to
                > > > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
                > > > > positive current input lead to a inversely decreasing output
                > > > > voltage
                > > > > relationship? Do any of the current sensors have a negative temp
                > > > > relationship?
                > > > >
                > > > > thanks
                > > > > Jerry
                > > > >
                >
                > [snip]
                >
                >
                > ------------------------------------
                >
                > Please trim excess when replyingYahoo! Groups Links
                >
                >
                >
              • jsternmd@att.net
                Big thanks Donald, i will dig into this to improve my learning on opamps. What software are you using for Spice models? I have a 30day trial of Multisim 12
                Message 7 of 18 , Jul 2, 2013
                  Big thanks Donald, i will dig into this to improve my learning on opamps. What software are you using for Spice models? I have a 30day trial of Multisim 12 but they want an Arm and Leg to buy it later.

                  best
                  jerry

                  --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:
                  >
                  > That image uses a different op amp but the results won't really change. There is also an LTspice circuit from which the jpg was snapped at <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1_LTspice.zip> if you'd like to try it yourself.
                  >
                  > Donald.
                  > --
                  > *Plain Text* email -- it's an accessibility issue
                  > () no proprietary attachments; no html mail
                  > /\ ascii ribbon campaign - <www.asciiribbon.org>
                  >
                  > ----- Original Message -----
                  > > From: "Donald H Locker" <dhlocker@...>
                  > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                  > > Sent: Tuesday, July 2, 2013 8:13:11 AM
                  > > Subject: Re: [Electronics_101] Re: What kind of Temperature Sensor is this ??
                  > > Hello, Jerry.
                  > >
                  > > <http://groups.yahoo.com/group/Electronics_101/files/Temp%20Sensor.pdf>
                  > > will show little or no change in voltages with changing temperature.
                  > > The noninverting input will always be at a high voltage (somewhere
                  > > between +5 and +12) and the opamp output will be high all the time.
                  > >
                  > > See the image (jpg) at
                  > > <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1.jpg>
                  > > for a circuit that will reproduces the 270mV at 4C, 290mV at 23C, and
                  > > 350mV at 84C values reported. (Those values will appear at the NonInv
                  > > node in this schematic.)
                  > >
                  > > Donald.
                  > > --
                  > > *Plain Text* email -- it's an accessibility issue
                  > > () no proprietary attachments; no html mail
                  > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                  > >
                  > > ----- Original Message -----
                  > > > From: jsternmd@...
                  > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                  > > > Sent: Monday, July 1, 2013 10:34:40 PM
                  > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                  > > > this ??
                  > > > HI Donald,
                  > > >
                  > > > I mapped out the schematic and uploaded it to the file section:
                  > > > named
                  > > > "Temperature Sensor Schematic". Does this match your thinking?
                  > > >
                  > > > thanks
                  > > > jerry
                  > > >
                  > > > --- In Electronics_101@yahoogroups.com, Donald H Locker
                  > > > <dhlocker@>
                  > > > wrote:
                  > > > >
                  > > > > Increasing positive current through the sensor increases the
                  > > > > voltage
                  > > > > across the 10k resistor. This is the same voltage that you would
                  > > > > read across the resistor with a voltmeter.
                  > > > >
                  > > > > This increasing voltage applied to the non-inverting input of the
                  > > > > op
                  > > > > amp causes the output voltage of the op amp to increase (because
                  > > > > vout = G(vnoninv - vinv) where G is a pretty large number - on the
                  > > > > order of thousands to tens of thousands). The output of the op amp
                  > > > > is connected to its inverting input (assuming a unity gain
                  > > > > configuration) and must rise sufficiently to bring the inverting
                  > > > > input up to the same voltage as the non-inverting input. The
                  > > > > result
                  > > > > is that the output voltage is [very nearly] the same voltage as
                  > > > > the
                  > > > > noninverting input which is the same as the inverting input (which
                  > > > > is connected to the output) even though the output and inverting
                  > > > > inputs are not connected to the sensor or the 10k resistor and
                  > > > > draw
                  > > > > no current from them.
                  > > > >
                  > > > > The current from the sensor does not go into the op amp, only
                  > > > > through the resistor to ground (to a pretty good approximation.)
                  > > > >
                  > > > > Donald.
                  > > > > --
                  > > > > *Plain Text* email -- it's an accessibility issue
                  > > > > () no proprietary attachments; no html mail
                  > > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                  > > > >
                  > > > > ----- Original Message -----
                  > > > > > From: jsternmd@
                  > > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                  > > > > > Sent: Monday, July 1, 2013 9:45:06 PM
                  > > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor
                  > > > > > is
                  > > > > > this ??
                  > > > > > Hi Donald,
                  > > > > >
                  > > > > > Let me ask a basic question. The output of the opamp shows
                  > > > > > increasing
                  > > > > > positive voltage with increasing temperature. The sensor input
                  > > > > > is
                  > > > > > to
                  > > > > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
                  > > > > > positive current input lead to a inversely decreasing output
                  > > > > > voltage
                  > > > > > relationship? Do any of the current sensors have a negative temp
                  > > > > > relationship?
                  > > > > >
                  > > > > > thanks
                  > > > > > Jerry
                  > > > > >
                  > >
                  > > [snip]
                  > >
                  > >
                  > > ------------------------------------
                  > >
                  > > Please trim excess when replyingYahoo! Groups Links
                  > >
                  > >
                  > >
                  >
                • Howard Hansen
                  Most people use LTspice. It is free and has a great support group. See:
                  Message 8 of 18 , Jul 2, 2013
                    Most people use LTspice. It is free and has a great support group. See:
                    <http://www.linear.com/designtools/software/#LTspice>
                    <http://tech.groups.yahoo.com/group/LTspice/>

                    The other Howard


                    On 7/2/2013 10:36 AM, jsternmd@... wrote:
                    >
                    > Big thanks Donald, i will dig into this to improve my learning on
                    > opamps. What software are you using for Spice models? I have a 30day
                    > trial of Multisim 12 but they want an Arm and Leg to buy it later.
                    >
                    > best
                    > jerry
                    >
                    > --- In Electronics_101@yahoogroups.com
                    > <mailto:Electronics_101%40yahoogroups.com>, Donald H Locker
                    > <dhlocker@...> wrote:
                    > >
                    > > That image uses a different op amp but the results won't really
                    > change. There is also an LTspice circuit from which the jpg was
                    > snapped at
                    > <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1_LTspice.zip>
                    > if you'd like to try it yourself.
                    > >
                    > > Donald.
                    > > -
                    >



                    [Non-text portions of this message have been removed]
                  • basicpoke
                    From what I can remember the last time I studied for interviews, to analyze an op-amp circuit you can assume: 1) The + and - input are at the same potential.
                    Message 9 of 18 , Jul 2, 2013
                      From what I can remember the last time I studied for interviews, to analyze an op-amp circuit you can assume: 1) The + and - input are at the same potential. 2) No current flows into the + and - input...So to get a feel for the circuit, you can assume the amp is gone and the + and - inputs are shorted. This can make it much easier to understand. Please correct me if I am wrong, or if there are other ways to simplify it.
                      Ron

                      --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:
                      >
                      > Increasing positive current through the sensor increases the voltage across the 10k resistor. This is the same voltage that you would read across the resistor with a voltmeter.
                      >
                      > This increasing voltage applied to the non-inverting input of the op amp causes the output voltage of the op amp to increase (because vout = G(vnoninv - vinv) where G is a pretty large number - on the order of thousands to tens of thousands). The output of the op amp is connected to its inverting input (assuming a unity gain configuration) and must rise sufficiently to bring the inverting input up to the same voltage as the non-inverting input. The result is that the output voltage is [very nearly] the same voltage as the noninverting input which is the same as the inverting input (which is connected to the output) even though the output and inverting inputs are not connected to the sensor or the 10k resistor and draw no current from them.
                      >
                      > The current from the sensor does not go into the op amp, only through the resistor to ground (to a pretty good approximation.)
                      >
                      > Donald.
                      > --
                      > *Plain Text* email -- it's an accessibility issue
                      > () no proprietary attachments; no html mail
                      > /\ ascii ribbon campaign - <www.asciiribbon.org>
                      >
                      > ----- Original Message -----
                      > > From: jsternmd@...
                      > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                      > > Sent: Monday, July 1, 2013 9:45:06 PM
                      > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
                      > > Hi Donald,
                      > >
                      > > Let me ask a basic question. The output of the opamp shows increasing
                      > > positive voltage with increasing temperature. The sensor input is to
                      > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
                      > > positive current input lead to a inversely decreasing output voltage
                      > > relationship? Do any of the current sensors have a negative temp
                      > > relationship?
                      > >
                      > > thanks
                      > > Jerry
                      > >
                      > > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@>
                      > > wrote:
                      > > >
                      > > > The current is converted to a voltage by the 10k load resistor
                      > > > (E=IR). Feeding that voltage to a non-inverting input of an op amp
                      > > > assures that the op-amp load does not affect the voltage. (The other
                      > > > alternative would to be to have the non-sensor end of the 10k
                      > > > resistor connected to a "virtual" ground at the inverting input of
                      > > > the op amp, and have the output go [more] negative as the input goes
                      > > > more positive. This sort of signal is not as easy for an A/D or
                      > > > requires another stage to invert again to a positive voltage.)
                      > > >
                      > > > No need for a microammeter; measuring the voltage across the 10k
                      > > > resistor is adequate, as you have done. That is exactly the kind of
                      > > > result I would expect for a current-output temperature sensor. A
                      > > > thermistor would be more non-linear over that range and a
                      > > > thermocouple's output is a millivolt-level that would not even show
                      > > > up on your measurements.
                      > > >
                      > > > Donald.
                      > > > --
                      > > > *Plain Text* email -- it's an accessibility issue
                      > > > () no proprietary attachments; no html mail
                      > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                      > > >
                      > > > ----- Original Message -----
                      > > > > From: jsternmd@
                      > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                      > > > > Sent: Sunday, June 30, 2013 9:55:45 PM
                      > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                      > > > > this ??
                      > > > >
                      > > > > Hi Donald, Stefan,
                      > > > >
                      > > > > I will try the series resistor experiment. I don't have a
                      > > > > microammeter
                      > > > > but its something I have wanted to add to my workbench. The AD950
                      > > > > or
                      > > > > other current device would be high impedance and limit changes in
                      > > > > current output with changes in supply voltage. Would you expect
                      > > > > the
                      > > > > mVDC per degree change I observed at the sensor output lead with a
                      > > > > current device?
                      > > > >
                      > > > > Also, would a current device make sense with the way this sensor
                      > > > > is
                      > > > > wired to the non-inverting input of the opamp? I am not too
                      > > > > experienced with opamps but I thought for a current to voltage
                      > > > > opamp
                      > > > > the input had to go to the inverting input to get a positive
                      > > > > voltage
                      > > > > output? The opamp output goes directly to an A-D input on a
                      > > > > PIC-type
                      > > > > uprocessor so I assume its a voltage to digital conversion.
                      > > > >
                      > > > > Many thanks again for your advice.
                      > > > >
                      > > > > jerry
                      > > > >
                      > > > > --- In Electronics_101@yahoogroups.com, Stefan Trethan
                      > > > > <stefan_trethan@> wrote:
                      > > > > >
                      > > > > > Making two measurements, say one with a 10k and one with a 20k
                      > > > > > resistor in series would determine if it is a current out device
                      > > > > > or
                      > > > > > a
                      > > > > > zener.
                      > > > > >
                      > > > > >
                      > > > > > ST
                      > > > > >
                      > > > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@>
                      > > > > > wrote:
                      > > > > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
                      > > > > > > is one possibility. There are other current-output temperature
                      > > > > > > sensors like this, though most I've seen are in larger
                      > > > > > > packages.
                      > > > > > >
                      > > > > > > HTH,
                      > > > > > > Donald.
                      > > > > > > --
                      > > > > >
                      > > > >
                      > > > >
                      > > > >
                      > > > >
                      > > > > ------------------------------------
                      > > > >
                      > > > > Please trim excess when replyingYahoo! Groups Links
                      > > > >
                      > > > >
                      > > > >
                      > > >
                      > >
                      > >
                      > >
                      > >
                      > > ------------------------------------
                      > >
                      > > Please trim excess when replyingYahoo! Groups Links
                      > >
                      > >
                      > >
                      >
                    • Derek
                      That is the best way to look at a voltage opamp. So long as the basic rules are followed, the rest is easy. Derek Koonce DDK Interactive Consulting Services
                      Message 10 of 18 , Jul 2, 2013
                        That is the best way to look at a voltage opamp. So long as the basic
                        rules are followed, the rest is easy.

                        Derek Koonce
                        DDK Interactive Consulting Services

                        On 7/2/2013 2:09 PM, basicpoke wrote:
                        >
                        > From what I can remember the last time I studied for interviews, to
                        > analyze an op-amp circuit you can assume: 1) The + and - input are at
                        > the same potential. 2) No current flows into the + and - input...So to
                        > get a feel for the circuit, you can assume the amp is gone and the +
                        > and - inputs are shorted. This can make it much easier to understand.
                        > Please correct me if I am wrong, or if there are other ways to
                        > simplify it.
                        > Ron
                        >
                        > --- In Electronics_101@yahoogroups.com
                        > <mailto:Electronics_101%40yahoogroups.com>, Donald H Locker
                        > <dhlocker@...> wrote:
                        > >
                        > > Increasing positive current through the sensor increases the voltage
                        > across the 10k resistor. This is the same voltage that you would read
                        > across the resistor with a voltmeter.
                        > >
                        > > This increasing voltage applied to the non-inverting input of the op
                        > amp causes the output voltage of the op amp to increase (because vout
                        > = G(vnoninv - vinv) where G is a pretty large number - on the order of
                        > thousands to tens of thousands). The output of the op amp is connected
                        > to its inverting input (assuming a unity gain configuration) and must
                        > rise sufficiently to bring the inverting input up to the same voltage
                        > as the non-inverting input. The result is that the output voltage is
                        > [very nearly] the same voltage as the noninverting input which is the
                        > same as the inverting input (which is connected to the output) even
                        > though the output and inverting inputs are not connected to the sensor
                        > or the 10k resistor and draw no current from them.
                        > >
                        > > The current from the sensor does not go into the op amp, only
                        > through the resistor to ground (to a pretty good approximation.)
                        > >
                        > > Donald.
                        > > --
                        > > *Plain Text* email -- it's an accessibility issue
                        > > () no proprietary attachments; no html mail
                        > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                        > >
                        > > ----- Original Message -----
                        > > > From: jsternmd@...
                        > > > To: "Electronics 101" <Electronics_101@yahoogroups.com
                        > <mailto:Electronics_101%40yahoogroups.com>>
                        > > > Sent: Monday, July 1, 2013 9:45:06 PM
                        > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                        > this ??
                        > > > Hi Donald,
                        > > >
                        > > > Let me ask a basic question. The output of the opamp shows increasing
                        > > > positive voltage with increasing temperature. The sensor input is to
                        > > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
                        > > > positive current input lead to a inversely decreasing output voltage
                        > > > relationship? Do any of the current sensors have a negative temp
                        > > > relationship?
                        > > >
                        > > > thanks
                        > > > Jerry
                        > > >
                        > > > --- In Electronics_101@yahoogroups.com
                        > <mailto:Electronics_101%40yahoogroups.com>, Donald H Locker <dhlocker@>
                        > > > wrote:
                        > > > >
                        > > > > The current is converted to a voltage by the 10k load resistor
                        > > > > (E=IR). Feeding that voltage to a non-inverting input of an op amp
                        > > > > assures that the op-amp load does not affect the voltage. (The other
                        > > > > alternative would to be to have the non-sensor end of the 10k
                        > > > > resistor connected to a "virtual" ground at the inverting input of
                        > > > > the op amp, and have the output go [more] negative as the input goes
                        > > > > more positive. This sort of signal is not as easy for an A/D or
                        > > > > requires another stage to invert again to a positive voltage.)
                        > > > >
                        > > > > No need for a microammeter; measuring the voltage across the 10k
                        > > > > resistor is adequate, as you have done. That is exactly the kind of
                        > > > > result I would expect for a current-output temperature sensor. A
                        > > > > thermistor would be more non-linear over that range and a
                        > > > > thermocouple's output is a millivolt-level that would not even show
                        > > > > up on your measurements.
                        > > > >
                        > > > > Donald.
                        > > > > --
                        > > > > *Plain Text* email -- it's an accessibility issue
                        > > > > () no proprietary attachments; no html mail
                        > > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                        > > > >
                        > > > > ----- Original Message -----
                        > > > > > From: jsternmd@
                        > > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com
                        > <mailto:Electronics_101%40yahoogroups.com>>
                        > > > > > Sent: Sunday, June 30, 2013 9:55:45 PM
                        > > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                        > > > > > this ??
                        > > > > >
                        > > > > > Hi Donald, Stefan,
                        > > > > >
                        > > > > > I will try the series resistor experiment. I don't have a
                        > > > > > microammeter
                        > > > > > but its something I have wanted to add to my workbench. The AD950
                        > > > > > or
                        > > > > > other current device would be high impedance and limit changes in
                        > > > > > current output with changes in supply voltage. Would you expect
                        > > > > > the
                        > > > > > mVDC per degree change I observed at the sensor output lead with a
                        > > > > > current device?
                        > > > > >
                        > > > > > Also, would a current device make sense with the way this sensor
                        > > > > > is
                        > > > > > wired to the non-inverting input of the opamp? I am not too
                        > > > > > experienced with opamps but I thought for a current to voltage
                        > > > > > opamp
                        > > > > > the input had to go to the inverting input to get a positive
                        > > > > > voltage
                        > > > > > output? The opamp output goes directly to an A-D input on a
                        > > > > > PIC-type
                        > > > > > uprocessor so I assume its a voltage to digital conversion.
                        > > > > >
                        > > > > > Many thanks again for your advice.
                        > > > > >
                        > > > > > jerry
                        > > > > >
                        > > > > > --- In Electronics_101@yahoogroups.com
                        > <mailto:Electronics_101%40yahoogroups.com>, Stefan Trethan
                        > > > > > <stefan_trethan@> wrote:
                        > > > > > >
                        > > > > > > Making two measurements, say one with a 10k and one with a 20k
                        > > > > > > resistor in series would determine if it is a current out device
                        > > > > > > or
                        > > > > > > a
                        > > > > > > zener.
                        > > > > > >
                        > > > > > >
                        > > > > > > ST
                        > > > > > >
                        > > > > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker <dhlocker@>
                        > > > > > > wrote:
                        > > > > > > >
                        > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
                        > > > > > > > is one possibility. There are other current-output temperature
                        > > > > > > > sensors like this, though most I've seen are in larger
                        > > > > > > > packages.
                        > > > > > > >
                        > > > > > > > HTH,
                        > > > > > > > Donald.
                        > > > > > > > --
                        > > > > > >
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > > > ------------------------------------
                        > > > > >
                        > > > > > Please trim excess when replyingYahoo! Groups Links
                        > > > > >
                        > > > > >
                        > > > > >
                        > > > >
                        > > >
                        > > >
                        > > >
                        > > >
                        > > > ------------------------------------
                        > > >
                        > > > Please trim excess when replyingYahoo! Groups Links
                        > > >
                        > > >
                        > > >
                        > >
                        >
                        >



                        [Non-text portions of this message have been removed]
                      • Howard Hansen
                        It looks like you have made an error in drawing the circuit diagram. If the temperature sensor is a constant current device and with the way you drew the
                        Message 11 of 18 , Jul 2, 2013
                          It looks like you have made an error in drawing the circuit diagram. If
                          the temperature sensor is a constant current device and with the way you
                          drew the circuit diagram the non inverting input to the op amp will
                          always be approximately 12 volts. This 12 volts will saturate the op
                          amp. Where as the circuit configuration recommended by Donald will work.

                          The other Howard


                          On 7/1/2013 9:34 PM, jsternmd@... wrote:
                          >
                          > HI Donald,
                          >
                          > I mapped out the schematic and uploaded it to the file section: named
                          > "Temperature Sensor Schematic". Does this match your thinking?
                          >
                          > thanks
                          > jerry
                          >



                          [Non-text portions of this message have been removed]
                        • Donald H Locker
                          Good so far. But the other important behaviour is that V_Out = Gain_OL * (V_NonInv - V_Inv) where Gain_OL is the open loop gain of the device. The two inputs
                          Message 12 of 18 , Jul 2, 2013
                            Good so far. But the other important behaviour is that "V_Out = Gain_OL * (V_NonInv - V_Inv)" where Gain_OL is the open loop gain of the device. The two inputs are truly only equal when Gain_OL is infinite and the op amp is operating in its linear range. Otherwise (the real-world case) there is some error but it's close enough for most work.

                            Donald.
                            --
                            *Plain Text* email -- it's an accessibility issue
                            () no proprietary attachments; no html mail
                            /\ ascii ribbon campaign - <www.asciiribbon.org>

                            ----- Original Message -----
                            > From: "basicpoke" <basicpoke@...>
                            > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                            > Sent: Tuesday, July 2, 2013 5:09:35 PM
                            > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
                            >
                            > From what I can remember the last time I studied for interviews, to
                            > analyze an op-amp circuit you can assume: 1) The + and - input are at
                            > the same potential. 2) No current flows into the + and - input...So to
                            > get a feel for the circuit, you can assume the amp is gone and the +
                            > and - inputs are shorted. This can make it much easier to understand.
                            > Please correct me if I am wrong, or if there are other ways to
                            > simplify it.
                            > Ron
                            >
                            > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...>
                            > wrote:
                            > >
                            > > Increasing positive current through the sensor increases the voltage
                            > > across the 10k resistor. This is the same voltage that you would
                            > > read across the resistor with a voltmeter.
                            > >
                            > > This increasing voltage applied to the non-inverting input of the op
                            > > amp causes the output voltage of the op amp to increase (because
                            > > vout = G(vnoninv - vinv) where G is a pretty large number - on the
                            > > order of thousands to tens of thousands). The output of the op amp
                            > > is connected to its inverting input (assuming a unity gain
                            > > configuration) and must rise sufficiently to bring the inverting
                            > > input up to the same voltage as the non-inverting input. The result
                            > > is that the output voltage is [very nearly] the same voltage as the
                            > > noninverting input which is the same as the inverting input (which
                            > > is connected to the output) even though the output and inverting
                            > > inputs are not connected to the sensor or the 10k resistor and draw
                            > > no current from them.
                            > >
                            > > The current from the sensor does not go into the op amp, only
                            > > through the resistor to ground (to a pretty good approximation.)
                            > >
                            > > Donald.
                            > > --
                            > > *Plain Text* email -- it's an accessibility issue
                            > > () no proprietary attachments; no html mail
                            > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                            > >
                            > > ----- Original Message -----
                            > > > From: jsternmd@...
                            > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                            > > > Sent: Monday, July 1, 2013 9:45:06 PM
                            > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor is
                            > > > this ??
                            > > > Hi Donald,
                            > > >
                            > > > Let me ask a basic question. The output of the opamp shows
                            > > > increasing
                            > > > positive voltage with increasing temperature. The sensor input is
                            > > > to
                            > > > pin 3 of the opamp which is noninverting. Wouldn't an increasing
                            > > > positive current input lead to a inversely decreasing output
                            > > > voltage
                            > > > relationship? Do any of the current sensors have a negative temp
                            > > > relationship?
                            > > >
                            > > > thanks
                            > > > Jerry
                            > > >
                            > > > --- In Electronics_101@yahoogroups.com, Donald H Locker
                            > > > <dhlocker@>
                            > > > wrote:
                            > > > >
                            > > > > The current is converted to a voltage by the 10k load resistor
                            > > > > (E=IR). Feeding that voltage to a non-inverting input of an op
                            > > > > amp
                            > > > > assures that the op-amp load does not affect the voltage. (The
                            > > > > other
                            > > > > alternative would to be to have the non-sensor end of the 10k
                            > > > > resistor connected to a "virtual" ground at the inverting input
                            > > > > of
                            > > > > the op amp, and have the output go [more] negative as the input
                            > > > > goes
                            > > > > more positive. This sort of signal is not as easy for an A/D or
                            > > > > requires another stage to invert again to a positive voltage.)
                            > > > >
                            > > > > No need for a microammeter; measuring the voltage across the 10k
                            > > > > resistor is adequate, as you have done. That is exactly the kind
                            > > > > of
                            > > > > result I would expect for a current-output temperature sensor. A
                            > > > > thermistor would be more non-linear over that range and a
                            > > > > thermocouple's output is a millivolt-level that would not even
                            > > > > show
                            > > > > up on your measurements.
                            > > > >
                            > > > > Donald.
                            > > > > --
                            > > > > *Plain Text* email -- it's an accessibility issue
                            > > > > () no proprietary attachments; no html mail
                            > > > > /\ ascii ribbon campaign - <www.asciiribbon.org>
                            > > > >
                            > > > > ----- Original Message -----
                            > > > > > From: jsternmd@
                            > > > > > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                            > > > > > Sent: Sunday, June 30, 2013 9:55:45 PM
                            > > > > > Subject: [Electronics_101] Re: What kind of Temperature Sensor
                            > > > > > is
                            > > > > > this ??
                            > > > > >
                            > > > > > Hi Donald, Stefan,
                            > > > > >
                            > > > > > I will try the series resistor experiment. I don't have a
                            > > > > > microammeter
                            > > > > > but its something I have wanted to add to my workbench. The
                            > > > > > AD950
                            > > > > > or
                            > > > > > other current device would be high impedance and limit changes
                            > > > > > in
                            > > > > > current output with changes in supply voltage. Would you
                            > > > > > expect
                            > > > > > the
                            > > > > > mVDC per degree change I observed at the sensor output lead
                            > > > > > with a
                            > > > > > current device?
                            > > > > >
                            > > > > > Also, would a current device make sense with the way this
                            > > > > > sensor
                            > > > > > is
                            > > > > > wired to the non-inverting input of the opamp? I am not too
                            > > > > > experienced with opamps but I thought for a current to voltage
                            > > > > > opamp
                            > > > > > the input had to go to the inverting input to get a positive
                            > > > > > voltage
                            > > > > > output? The opamp output goes directly to an A-D input on a
                            > > > > > PIC-type
                            > > > > > uprocessor so I assume its a voltage to digital conversion.
                            > > > > >
                            > > > > > Many thanks again for your advice.
                            > > > > >
                            > > > > > jerry
                            > > > > >
                            > > > > > --- In Electronics_101@yahoogroups.com, Stefan Trethan
                            > > > > > <stefan_trethan@> wrote:
                            > > > > > >
                            > > > > > > Making two measurements, say one with a 10k and one with a
                            > > > > > > 20k
                            > > > > > > resistor in series would determine if it is a current out
                            > > > > > > device
                            > > > > > > or
                            > > > > > > a
                            > > > > > > zener.
                            > > > > > >
                            > > > > > >
                            > > > > > > ST
                            > > > > > >
                            > > > > > > On Sun, Jun 30, 2013 at 10:12 PM, Donald H Locker
                            > > > > > > <dhlocker@>
                            > > > > > > wrote:
                            > > > > > > > <http://www.analog.com/en/mems-sensors/digital-temperature-sensors/ad590/products/product.html>
                            > > > > > > > is one possibility. There are other current-output
                            > > > > > > > temperature
                            > > > > > > > sensors like this, though most I've seen are in larger
                            > > > > > > > packages.
                            > > > > > > >
                            > > > > > > > HTH,
                            > > > > > > > Donald.
                            > > > > > > > --
                            > > > > > >
                            > > > > >
                            > > > > >
                            > > > > >
                            > > > > >
                            > > > > > ------------------------------------
                            > > > > >
                            > > > > > Please trim excess when replyingYahoo! Groups Links
                            > > > > >
                            > > > > >
                            > > > > >
                            > > > >
                            > > >
                            > > >
                            > > >
                            > > >
                            > > > ------------------------------------
                            > > >
                            > > > Please trim excess when replyingYahoo! Groups Links
                            > > >
                            > > >
                            > > >
                            > >
                            >
                            >
                            >
                            >
                            > ------------------------------------
                            >
                            > Please trim excess when replyingYahoo! Groups Links
                            >
                            >
                            >
                          • jsternmd@att.net
                            I went back to the drawing board or in this case the actual PCB since no schematic is available. Based on your explanation, I did miss one resistor --- there
                            Message 13 of 18 , Jul 2, 2013
                              I went back to the drawing board or in this case the actual PCB since no schematic is available. Based on your explanation, I did miss one resistor --- there indeed is a 10k in series between the sensor output and the opamp +input, however there is also a 1K from the sensor output to ground ! So now it makes sense, as you said virtually all current goes to ground via the 1k. For the AD590 at 273K (=0 C) = 273uA, the voltage would be 273mV exactly what I found experimentally !

                              Many thanks for your patience and clear explanations. I downloaded LTSpice and will start that learning curve.

                              jerry



                              --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...> wrote:
                              >
                              > Most people use LTspice. It is free and has a great support group. See:
                              > <http://www.linear.com/designtools/software/#LTspice>
                              > <http://tech.groups.yahoo.com/group/LTspice/>
                              >
                              > The other Howard
                              >
                              >
                              > On 7/2/2013 10:36 AM, jsternmd@... wrote:
                              > >
                              > > Big thanks Donald, i will dig into this to improve my learning on
                              > > opamps. What software are you using for Spice models? I have a 30day
                              > > trial of Multisim 12 but they want an Arm and Leg to buy it later.
                              > >
                              > > best
                              > > jerry
                              > >
                              > > --- In Electronics_101@yahoogroups.com
                              > > <mailto:Electronics_101%40yahoogroups.com>, Donald H Locker
                              > > <dhlocker@> wrote:
                              > > >
                              > > > That image uses a different op amp but the results won't really
                              > > change. There is also an LTspice circuit from which the jpg was
                              > > snapped at
                              > > <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1_LTspice.zip>
                              > > if you'd like to try it yourself.
                              > > >
                              > > > Donald.
                              > > > -
                              > >
                              >
                              >
                              >
                              > [Non-text portions of this message have been removed]
                              >
                            • Donald H Locker
                              Cool! (so to speak.) Enjoy the ride. Donald. -- *Plain Text* email -- it s an accessibility issue () no proprietary attachments; no html mail / ascii ribbon
                              Message 14 of 18 , Jul 2, 2013
                                Cool! (so to speak.) Enjoy the ride.

                                Donald.
                                --
                                *Plain Text* email -- it's an accessibility issue
                                () no proprietary attachments; no html mail
                                /\ ascii ribbon campaign - <www.asciiribbon.org>

                                ----- Original Message -----
                                > From: jsternmd@...
                                > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                                > Sent: Tuesday, July 2, 2013 8:39:25 PM
                                > Subject: [Electronics_101] Re: What kind of Temperature Sensor is this ??
                                > I went back to the drawing board or in this case the actual PCB since
                                > no schematic is available. Based on your explanation, I did miss one
                                > resistor --- there indeed is a 10k in series between the sensor output
                                > and the opamp +input, however there is also a 1K from the sensor
                                > output to ground ! So now it makes sense, as you said virtually all
                                > current goes to ground via the 1k. For the AD590 at 273K (=0 C) =
                                > 273uA, the voltage would be 273mV exactly what I found experimentally
                                > !
                                >
                                > Many thanks for your patience and clear explanations. I downloaded
                                > LTSpice and will start that learning curve.
                                >
                                > jerry
                                >
                                >
                                >
                                > --- In Electronics_101@yahoogroups.com, Howard Hansen <hrhan@...>
                                > wrote:
                                > >
                                > > Most people use LTspice. It is free and has a great support group.
                                > > See:
                                > > <http://www.linear.com/designtools/software/#LTspice>
                                > > <http://tech.groups.yahoo.com/group/LTspice/>
                                > >
                                > > The other Howard
                                > >
                                > >
                                > > On 7/2/2013 10:36 AM, jsternmd@... wrote:
                                > > >
                                > > > Big thanks Donald, i will dig into this to improve my learning on
                                > > > opamps. What software are you using for Spice models? I have a
                                > > > 30day
                                > > > trial of Multisim 12 but they want an Arm and Leg to buy it later.
                                > > >
                                > > > best
                                > > > jerry
                                > > >
                                > > > --- In Electronics_101@yahoogroups.com
                                > > > <mailto:Electronics_101%40yahoogroups.com>, Donald H Locker
                                > > > <dhlocker@> wrote:
                                > > > >
                                > > > > That image uses a different op amp but the results won't really
                                > > > change. There is also an LTspice circuit from which the jpg was
                                > > > snapped at
                                > > > <http://groups.yahoo.com/group/Electronics_101/files/Temp_Sensor_1_LTspice.zip>
                                > > > if you'd like to try it yourself.
                                > > > >
                                > > > > Donald.
                                > > > > -
                                > > >
                                > >
                                > >
                                > >
                                > > [Non-text portions of this message have been removed]
                                > >
                                >
                                >
                                >
                                >
                                > ------------------------------------
                                >
                                > Please trim excess when replyingYahoo! Groups Links
                                >
                                >
                                >
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