Connect with us

Question about Thermocouple

Discussion in 'Electronic Basics' started by K Wind, Aug 31, 2003.

Scroll to continue with content
  1. K Wind

    K Wind Guest

    I want to build a cold compensation circuit for a type K thermocouple that I
    have. The two wires are soldered together at the end. I plan on using
    boiling water and ice water to calibrate. Can I put the end of the probe
    into the water just the way it is?

  2. John Larkin

    John Larkin Guest

    Sure. But make sure the cold cal is done with lots of well-crushed
    ice, stirred frequently. Just some ice cubes in a glass of water can
    be pretty far off. And adjust your boiling point for altitude.

  3. Garrett Mace

    Garrett Mace Guest

    I think he's worried about the conductivity of the water throwing off the
    measurements, since the wires are bare. I've not had any experience with
    thermocouples either; is the difference significant, or should he use
    distilled water?

    I would guess if he is using ice and boiling water as reference points, he's
    not trying to be terribly accurate.
  4. Guest

    Guest Guest

    You can calibrate the uninsulated thermocouple by immersing it in water.
    The only problem that may occur is if there is any continuity between the
    water and some other part of the circuit
    e.g. grounded tea kettle containing the water having same ground as measurement

    If your circuit is battery powered this isn't an issue.

    An ice bath made with a distilled ice water bath makes a very accurate zero
    calibration point.

    The boiling water is a different story.
    As mentioned before you have to compensate for altitude.

    Long story shot, calibrate your zero with the ice water and the span with
    boiling water and you will get reasonable accuracy.

  5. John Larkin

    John Larkin Guest

    I've read the claim that an ice bath made with almost any common tap
    water will be within 5 or so millikelvins of zero C, if done
    carefully. A thermos bottle, lots finely crushed ice, and enthusiastic
    stirring is needed.

  6. K Wind

    K Wind Guest

    I actually have two thermocouples. One is welded and the other is bead
    welded. If I'm not mistaken, isn't bead welded another name for silver

    Anyway, what does your answer have to do with whether or not I can put the
    damn thing in water?

  7. Bob Masta

    Bob Masta Guest

    Somewhere on the Web I found a description of how to weld
    with a car battery and the inside of an old dry cell... tried it and
    it works great! You need to pull the carbon rod from an
    ordinary (not alkaline) cell. Twist the TC wires together and
    clamp the ground from a jumper cable to the twist, near as
    practical to the end but not _too_ close. Clamp the positive
    lead of the jumpers onto the carbon rod. Then bring the
    twisted end of the TC to the rod with a gentle stroke, and
    presto...nicely welded TC!

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Shareware from Interstellar Research
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day