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Re: [hobbicast] Digest Number 3811

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  • CaptonZap@aol.com
    In a message dated 1/5/2012 3:03:01 A.M. Mountain Standard Time, hobbicast@yahoogroups.com writes: LIke I said - its *really* simple. It just measures the
    Message 1 of 4 , Jan 5, 2012
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      In a message dated 1/5/2012 3:03:01 A.M. Mountain Standard Time,
      hobbicast@yahoogroups.com writes:

      LIke I said - its *really* simple. It just measures the resistance of the
      wire - which is the probe.


      Uhh, you better go back and try reading again.
      The thermocouple junction actually generates a voltage as heat is applied.
      The hotter the heat, the higher the voltage. Or should I say micro voltage.
      You are describing a thermister, which is a different animal. CZ




      [Non-text portions of this message have been removed]
    • Jeshua Lacock
      ... My apologies. Last time I read about the details was several years ago and I was going off my memory. Reading the voltage is not much different than
      Message 2 of 4 , Jan 5, 2012
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        On Jan 5, 2012, at 9:02 AM, CaptonZap@... wrote:

        > Uhh, you better go back and try reading again.
        > The thermocouple junction actually generates a voltage as heat is applied.
        > The hotter the heat, the higher the voltage. Or should I say micro voltage.
        > You are describing a thermister, which is a different animal. CZ

        My apologies. Last time I read about the details was several years ago and I was going off my memory.

        Reading the voltage is not much different than reading the resistance - I mean they are both very simple tasks for a multimeter and over years could easily be confused.


        Best,

        Jeshua Lacock
        Founder/Engineer
        3DTOPO Incorporated
        <http://3DTOPO.com>
        Phone: 208.462.4171
      • Glenn N
        The thermocouple junction is also 2 different metals welded together. The thermal/electrical characteristics are dependant on the 2 wires chosen. Then you
        Message 3 of 4 , Jan 5, 2012
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          The thermocouple junction is also 2 different metals welded together. The
          thermal/electrical characteristics are dependant on the 2 wires chosen.
          Then you have to use wire that has a high enough melting point to work in
          that environment and calibrate the resistance of the connecting wire so you
          know the IR drop from the junction to the meter. Making a thermocouple is
          fairly simple. Making one to function reliably at 3000F* is a different
          matter.
          Do they make cones that go that high?
          Glenn
          ----- Original Message -----
          From: <CaptonZap@...>
          To: <hobbicast@yahoogroups.com>
          Sent: Thursday, January 05, 2012 8:02 AM
          Subject: Re: [hobbicast] Digest Number 3811




          In a message dated 1/5/2012 3:03:01 A.M. Mountain Standard Time,
          hobbicast@yahoogroups.com writes:

          LIke I said - its *really* simple. It just measures the resistance of the
          wire - which is the probe.


          Uhh, you better go back and try reading again.
          The thermocouple junction actually generates a voltage as heat is applied.
          The hotter the heat, the higher the voltage. Or should I say micro voltage.
          You are describing a thermister, which is a different animal. CZ




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



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        • Evan Daniel
          The meter should be measuring voltage; there should be no current flow, and thus no IR voltage drop. Thermocouple meters are just (micro)volt meters with a
          Message 4 of 4 , Jan 5, 2012
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            The meter should be measuring voltage; there should be no current
            flow, and thus no IR voltage drop. Thermocouple meters are just
            (micro)volt meters with a volt/temperature calibration curve, plus
            compensation for the cold junction temperature. (The thermocouple
            measures relative temperature between the two ends; you need to know
            the temp of one end to get absolute temperature.)

            For aluminum casting work, I use a type K thermocouple in a ceramic
            sheath purchased from McMaster-Carr. I use an ordinary DMM that
            happens to have a thermocouple input to read it. ($40 at harbor
            Freight; about $60 for probe, sheath, extension wire, and a couple
            connectors.)

            Evan Daniel

            On Thu, Jan 5, 2012 at 1:35 PM, Glenn N <sleykin@...> wrote:
            > The thermocouple junction is also 2 different metals welded together.  The
            > thermal/electrical characteristics are dependant on the 2 wires chosen.
            > Then you have to use wire that has a high enough melting point to work in
            > that environment and calibrate the resistance of the connecting wire so you
            > know the IR drop from the junction to the meter.  Making a thermocouple is
            > fairly simple.  Making one to function reliably at 3000F* is a different
            > matter.
            > Do they make cones that go that high?
            > Glenn
            > ----- Original Message -----
            > From: <CaptonZap@...>
            > To: <hobbicast@yahoogroups.com>
            > Sent: Thursday, January 05, 2012 8:02 AM
            > Subject: Re: [hobbicast] Digest Number 3811
            >
            >
            >
            >
            > In a message dated 1/5/2012 3:03:01 A.M. Mountain Standard Time,
            > hobbicast@yahoogroups.com writes:
            >
            > LIke I  said - its *really* simple. It just measures the resistance of the
            > wire -  which is the probe.
            >
            >
            > Uhh, you better go back and try reading again.
            > The thermocouple junction actually generates a voltage as heat is applied.
            > The hotter the heat, the higher the voltage. Or should I say micro  voltage.
            > You are describing a thermister, which is a different animal.   CZ
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            > ------------------------------------
            >
            > For discussion of Metal Casting and related issues
            > this list does not accept attachments.
            >
            > Files area and list services are at:
            >     http://groups.yahoo.com/group/hobbicast
            >
            > For additional files and photos and off topic discussions
            > check out these two affiliated sites:
            >     http://groups.yahoo.com/group/sandcrabs
            >     http://groups.yahoo.com/group/Hobbicast1
            >
            > Please visit our sponsor: Budget Casting Supply
            > http://budgetcastingsupply.com/
            >
            > List Owner:
            > owly@...
            >
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            > ------------------------------------
            >
            > For discussion of Metal Casting and related issues
            > this list does not accept attachments.
            >
            > Files area and list services are at:
            >     http://groups.yahoo.com/group/hobbicast
            >
            > For additional files and photos and off topic discussions
            > check out these two affiliated sites:
            >     http://groups.yahoo.com/group/sandcrabs
            >     http://groups.yahoo.com/group/Hobbicast1
            >
            > Please visit our sponsor: Budget Casting Supply
            > http://budgetcastingsupply.com/
            >
            > List Owner:
            > owly@...
            >
            > Yahoo! Groups Links
            >
            >
            >
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