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Re: [Electronics_101] Re: Thermal Imagers to Find Circuit Fault

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  • Stefan Trethan
    Do not confuse the near IR light from a remote control with thermal IR. A remote control has about 1000nm, thermal radiation at reasonable temperatures about
    Message 1 of 20 , Jun 12, 2013
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      Do not confuse the near IR light from a remote control with thermal IR.
      A remote control has about 1000nm, thermal radiation at reasonable
      temperatures about 10000nm.

      A regular sensor and regular optics will _not_ make a thermal image at
      the temperatures in question.
      You could only look at very hot components that are well on the way to
      producing visible light (incandescence).

      If you have proof, as in a real thermal image taken with such a cheap
      camera, provide it, until then I will not believe you.

      I quote from wikipedia:

      Non-specialized CCD and CMOS sensors have most of their spectral
      sensitivity in the visible light wavelength range. However by
      utilizing the "trailing" area of their spectral sensitivity, namely
      the part of the infrared spectrum called near-infrared (NIR), and by
      using off-the-shelf CCTV camera it is possible under certain
      circumstances to obtain true thermal images of objects with
      temperatures at about 280°C and higher.[2]
      <https://en.wikipedia.org/wiki/Thermography>


      ST



      On Wed, Jun 12, 2013 at 7:08 PM, Andrew Mathison (Alice)
      <mathison@...> wrote:
      > Actually, what you posted is simply not true in the way that we need it
      > here, though technically for high end prices and exact measurement you may
      > be right!
      >
      > Simply put, there are many cameras around that are sensitive to ANY IR, for
      > instance Sony produces Video cameras with "Nightshot" and an extra switch
      > for "Super Nightshot" that are REALLY sensitive to varying temperatures,
      > they can make great "green and black" videos/pictures in perfect darkness as
      > long as there is a human nearby or any source of ANY TYPE OF IR...
      >
      > I have such a video camera from Sony that is truly fantastic on pitch black
      > nights..I am told that later ones are not quite as good, but must still be
      > good enough for what we need I would guess.
      >
      > You seem to forget that we are not trying to measure a temperature exactly,
      > though someone who took the time to calibrate his video camera in some way
      > (I have some ideas on the subject if anyone is interested), might eventually
      > be able to say exactly what the temperature was, but we here do not need
      > that, we only need to see a "difference".
      >
      > A hot component will stick out like a sore thumb (maybe give you a sore
      > thumb if you touch it!!)...as a very bright green "lit" object..So the idea
      > is really good to try and use such a camera for such work.
      >
      > Almost any (I think actually ALL is correct there) modern digital camera
      > will show you clearly for instance if an IR remote control is working or
      > not, just press the buttons and look at the IR LED to see if it blinks or
      > not through the camera! I have checked out suspect remotes in this way for
      > the last 10-15 years on several different cameras from different
      > manufacturers...Any of you with a digital camera can easily check what I am
      > saying (provided you have an IR Remote control as well :-) )
      >
      > Whether or not it is accurate and sensitive enough to spot a hot component,
      > some of you here can easily find out, all they need is to try it, but as
      > someone said, there is an IR filter in most cameras that reduces the
      > sensitivity to IR dramatically in some units..
      >
      > If you have an older digital camera that still works, but you don't need,
      > take it apart and remove the filter, fine tools and a steady hand are needed
      > and there are also some videos showing how on YouTube. That way, a hot
      > component can be easily and cheaply identified...
      >
      > Sony is a good place to start, but most cameras should work I believe.
      >
      > You say that glass blocks IR, but surely it is not complete, it's certainly
      > not enough to make any difference noticeable to my Sony, therefore it could
      > possibly have plastic lenses, but they do sound like glass when I tap them
      > carefully...more than that I will not try!!
      >
      > Regards
      >
      > Andy
      >
    • Andrew Mathison (Alice)
      My Sony video camera, with no changes to it, except to switch on the NightShot feature works fine in complete darkness... I can place a piece of black
      Message 2 of 20 , Jun 13, 2013
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        My Sony video camera, with no changes to it, except to switch on the
        "NightShot" feature works fine in complete darkness...

        I can place a piece of black (exposed) film or even a piece cut out from an
        old floppy disk, over my Sony lens to block all normal light and see great
        images in heat only...things like candles burning make a very intense light.


        Why would a hot component not do the same?

        I know not all cameras with the IR filter still in place will see anything
        with the black filter also in place, but some Sony cameras are well known
        for being able to do this.

        But a hot component, in a darkened room will be seen clearly on many cameras
        I am sure..If I think of an easy way to simulate this, I will try it using
        an unmodified Canon Digital Camera this weekend.

        Surely a few others could try to see something hot in a dark room with their
        digital camera, a few others could try removing the filter on an old working
        one and report the effects here.?

        I am sure that we all working together (plus a few old cameras getting
        modded as well), we can end up with a great tool for "seeing" hot components
        without giving out a lot of money...

        Regards

        Andy




        [Non-text portions of this message have been removed]
      • Stefan Trethan
        People have been there, done that. It does not work for good technical reasons. You may see objects that have several hundred degrees, but you will never see
        Message 3 of 20 , Jun 13, 2013
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          People have been there, done that. It does not work for good technical reasons.
          You may see objects that have several hundred degrees, but you will
          never see anything with say 100°C, it's just not physically possible.

          Believe me, I would be the first to modify a camera if there was any
          possiblity or evidence that this would work.

          If you look on the web you will find some cheap thermal imagers made
          by scanning with a single point infrared thermometer.
          Takes long to make a single shot, but it is relatively cheap if your
          time is free.

          You will also find references to something called a "thermal
          flashlight" which is a thermometer connected to a multi-colour LED.
          This way you can take a long exposure while moving your sensor around,
          resulting in a thermal image of sorts.

          Both approaches would work to find hot components on a PCB, but not
          really that much better than feeling around or searching with a
          thermometer.


          ST




          On Thu, Jun 13, 2013 at 4:07 PM, Andrew Mathison (Alice)
          <mathison@...> wrote:
          > My Sony video camera, with no changes to it, except to switch on the
          > "NightShot" feature works fine in complete darkness...
          >
          > I can place a piece of black (exposed) film or even a piece cut out from an
          > old floppy disk, over my Sony lens to block all normal light and see great
          > images in heat only...things like candles burning make a very intense light.
          >
          >
          > Why would a hot component not do the same?
          >
          > I know not all cameras with the IR filter still in place will see anything
          > with the black filter also in place, but some Sony cameras are well known
          > for being able to do this.
          >
          > But a hot component, in a darkened room will be seen clearly on many cameras
          > I am sure..If I think of an easy way to simulate this, I will try it using
          > an unmodified Canon Digital Camera this weekend.
          >
          > Surely a few others could try to see something hot in a dark room with their
          > digital camera, a few others could try removing the filter on an old working
          > one and report the effects here.?
          >
          > I am sure that we all working together (plus a few old cameras getting
          > modded as well), we can end up with a great tool for "seeing" hot components
          > without giving out a lot of money...
          >
          > Regards
          >
          > Andy
          >
          >
        • Terrance
          Perhaps it is an issue of what temperature range is of interest. I also have a Sony camera from the 90s with the NightShot and Super NightShot
          Message 4 of 20 , Jun 13, 2013
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            Perhaps it is an issue of what temperature range is of interest. I also have a Sony camera from the 90s with the NightShot and Super NightShot abilities...your post prompted me to do some testing. I took two identical pieces of black anodized aluminum (~1cmx4cmx10cm), heated one to 100C (suspended in boiling water) and left the other at room temp (around 20C). In a darkened room they looked identical through my viewfinder. Since I have no need to measure temperatures in this way over about 150C, this is just not going to be useful to me.

            Reminded me how nifty of an effect those old NightShot video cameras make though...my newer cameras don't have anything like that, weird. On my old Sony, the SuperNightShot mode just seems to turn on an IR LED above the lens.

            -Terrance

            --- In Electronics_101@yahoogroups.com, "Andrew Mathison \(Alice\)" <mathison@...> wrote:
            >
            > My Sony video camera, with no changes to it, except to switch on the
            > "NightShot" feature works fine in complete darkness...
            >
            > I can place a piece of black (exposed) film or even a piece cut out from an
            > old floppy disk, over my Sony lens to block all normal light and see great
            > images in heat only...things like candles burning make a very intense light.
            >
            >
            > Why would a hot component not do the same?
            >
            > I know not all cameras with the IR filter still in place will see anything
            > with the black filter also in place, but some Sony cameras are well known
            > for being able to do this.
            >
            > But a hot component, in a darkened room will be seen clearly on many cameras
            > I am sure..If I think of an easy way to simulate this, I will try it using
            > an unmodified Canon Digital Camera this weekend.
            >
            > Surely a few others could try to see something hot in a dark room with their
            > digital camera, a few others could try removing the filter on an old working
            > one and report the effects here.?
            >
            > I am sure that we all working together (plus a few old cameras getting
            > modded as well), we can end up with a great tool for "seeing" hot components
            > without giving out a lot of money...
            >
            > Regards
            >
            > Andy
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
          • Stefan Trethan
            Perhaps the current sensors are not as suitable to night shooting as the old ones were? Modern cameras have other advantages... ST
            Message 5 of 20 , Jun 13, 2013
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              Perhaps the current sensors are not as suitable to night shooting as
              the old ones were?

              Modern cameras have other advantages...

              ST

              On Thu, Jun 13, 2013 at 5:23 PM, Terrance <evilterrance@...> wrote:

              > Reminded me how nifty of an effect those old NightShot video cameras make though...my newer cameras don't have anything like that, weird. On my old Sony, the SuperNightShot mode just seems to turn on an IR LED above the lens.
              >
              > -Terrance
              >
            • Derek
              The image may be there, but it would be very faint. One would have to look at the blackbody curve and observe the amount of energy radiating in the band
              Message 6 of 20 , Jun 13, 2013
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                The image may be there, but it would be very faint. One would have to
                look at the blackbody curve and observe the amount of energy radiating
                in the band between the wavelength where floppy disk passes light and
                the wavelength where glass absorbs. There will not be much energy in
                this band to notice. A candle or other appropriate hot object has much
                more energy in this band. Thus you would see it on the camera.

                Essentially the use of the floppy disk and the glass of the camera lens
                act as a band-pass filter system. Not in the electronic sense, but in
                the electromagnetic spectrum sense - optical in this case.

                Glass cut-off is around 3 microns. But a bit of hunting shows that the
                floppy disc looks to have a pass band from 0.75 microns to 1.5 microns.
                Red side of the visible spectrum is around 0.7 microns.

                Now, looking at the blackbody radiation curve for something around 400K
                (100C) to 3000K (light a light bulb / flame) you will see essentially no
                radiation in this band of 0.75 to 1.5 for the low temp, and much
                radiation for the higher temp. One calculator I found that provides the
                curve can be found at
                http://www.spectralcalc.com/blackbody_calculator/blackbody.php
                Be sure to look at the area under the curve and see the change. Use the
                band range to clearly see the difference.

                Hope this explains the optical side of the world. And yes, I have done
                much in electro-optics over the years.

                Derek Koonce
                DDK Interactive Consulting Services


                On 6/13/2013 7:07 AM, Andrew Mathison (Alice) wrote:
                >
                > My Sony video camera, with no changes to it, except to switch on the
                > "NightShot" feature works fine in complete darkness...
                >
                > I can place a piece of black (exposed) film or even a piece cut out
                > from an
                > old floppy disk, over my Sony lens to block all normal light and see great
                > images in heat only...things like candles burning make a very intense
                > light.
                >
                > Why would a hot component not do the same?
                >
                > I know not all cameras with the IR filter still in place will see anything
                > with the black filter also in place, but some Sony cameras are well known
                > for being able to do this.
                >
                > But a hot component, in a darkened room will be seen clearly on many
                > cameras
                > I am sure..If I think of an easy way to simulate this, I will try it using
                > an unmodified Canon Digital Camera this weekend.
                >
                > Surely a few others could try to see something hot in a dark room with
                > their
                > digital camera, a few others could try removing the filter on an old
                > working
                > one and report the effects here.?
                >
                > I am sure that we all working together (plus a few old cameras getting
                > modded as well), we can end up with a great tool for "seeing" hot
                > components
                > without giving out a lot of money...
                >
                > Regards
                >
                > Andy
                >
                >
                >
                > [Non-text portions of this message have been removed]
                >
                >



                [Non-text portions of this message have been removed]
              • Derek
                Night shot mode of cameras is looking for IR reflections, hence the night lamp options. I just posted reasoning of what is visible and not based on
                Message 7 of 20 , Jun 13, 2013
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                  Night shot mode of cameras is looking for IR reflections, hence the
                  night lamp options. I just posted reasoning of what is visible and not
                  based on electro-optics.

                  Derek Koonce
                  DDK Interactive Consulting Services

                  On 6/13/2013 8:23 AM, Terrance wrote:
                  >
                  > Perhaps it is an issue of what temperature range is of interest. I
                  > also have a Sony camera from the 90s with the NightShot and Super
                  > NightShot abilities...your post prompted me to do some testing. I took
                  > two identical pieces of black anodized aluminum (~1cmx4cmx10cm),
                  > heated one to 100C (suspended in boiling water) and left the other at
                  > room temp (around 20C). In a darkened room they looked identical
                  > through my viewfinder. Since I have no need to measure temperatures in
                  > this way over about 150C, this is just not going to be useful to me.
                  >
                  > Reminded me how nifty of an effect those old NightShot video cameras
                  > make though...my newer cameras don't have anything like that, weird.
                  > On my old Sony, the SuperNightShot mode just seems to turn on an IR
                  > LED above the lens.
                  >
                  > -Terrance
                  >
                  > --- In Electronics_101@yahoogroups.com
                  > <mailto:Electronics_101%40yahoogroups.com>, "Andrew Mathison
                  > \(Alice\)" <mathison@...> wrote:
                  > >
                  > > My Sony video camera, with no changes to it, except to switch on the
                  > > "NightShot" feature works fine in complete darkness...
                  > >
                  > > I can place a piece of black (exposed) film or even a piece cut out
                  > from an
                  > > old floppy disk, over my Sony lens to block all normal light and see
                  > great
                  > > images in heat only...things like candles burning make a very
                  > intense light.
                  > >
                  > >
                  > > Why would a hot component not do the same?
                  > >
                  > > I know not all cameras with the IR filter still in place will see
                  > anything
                  > > with the black filter also in place, but some Sony cameras are well
                  > known
                  > > for being able to do this.
                  > >
                  > > But a hot component, in a darkened room will be seen clearly on many
                  > cameras
                  > > I am sure..If I think of an easy way to simulate this, I will try it
                  > using
                  > > an unmodified Canon Digital Camera this weekend.
                  > >
                  > > Surely a few others could try to see something hot in a dark room
                  > with their
                  > > digital camera, a few others could try removing the filter on an old
                  > working
                  > > one and report the effects here.?
                  > >
                  > > I am sure that we all working together (plus a few old cameras getting
                  > > modded as well), we can end up with a great tool for "seeing" hot
                  > components
                  > > without giving out a lot of money...
                  > >
                  > > Regards
                  > >
                  > > Andy
                  > >
                  > >
                  > >
                  > >
                  > > [Non-text portions of this message have been removed]
                  > >
                  >
                  >



                  [Non-text portions of this message have been removed]
                • Derek
                  There are detectors that will work in the higher wavelength, far infrared. They typically need to be cooled to function properly and not provide false images.
                  Message 8 of 20 , Jun 13, 2013
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                    There are detectors that will work in the higher wavelength, far
                    infrared. They typically need to be cooled to function properly and not
                    provide false images. I use to use liquid nitrogen to cool the sensors,
                    but now with the thermal electric coolers, the days of liquid nitrogen
                    is gone - unless getting way out in the infrared portion.

                    Derek Koonce
                    DDK Interactive Consulting Services


                    On 6/13/2013 9:02 AM, Stefan Trethan wrote:
                    >
                    > Perhaps the current sensors are not as suitable to night shooting as
                    > the old ones were?
                    >
                    > Modern cameras have other advantages...
                    >
                    > ST
                    >
                    > On Thu, Jun 13, 2013 at 5:23 PM, Terrance <evilterrance@...
                    > <mailto:evilterrance%40hotmail.com>> wrote:
                    >
                    > > Reminded me how nifty of an effect those old NightShot video cameras
                    > make though...my newer cameras don't have anything like that, weird.
                    > On my old Sony, the SuperNightShot mode just seems to turn on an IR
                    > LED above the lens.
                    > >
                    > > -Terrance
                    > >
                    >
                    >



                    [Non-text portions of this message have been removed]
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