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Best portable multichannel thermocouple thermometer

Discussion in 'Electronic Design' started by Phil Hobbs, Dec 31, 2013.

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  1. Phil Hobbs

    Phil Hobbs Guest

    Hi, all,

    One of my gizmos that I transferred to a contract engineering outfit in
    Orange County CA is having a few teething troubles, which my original
    prototype didn't exhibit. I suspect that it's largely due to thermal
    drift, either in the circuitry, the light source or the alignment.

    To test this, I need to get a thermocouple thermometer that is good and
    rugged, can measure at least two channels and preferably four, and is as
    accurate as you can reasonably do with a thermocouple, maybe 0.25 to 0.5
    degrees C. The temperature range is maybe 0 to 100 C. Extra credit for
    isolated channels, and for being able to go to 250C so I can measure the
    bulb envelope temperature, at least at some level.

    Budget is probably $500.



    Phil Hobbs

    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
  2. Den tirsdag den 31. december 2013 02.16.32 UTC+1 skrev Phil Hobbs:
    fluke 52 or fluke 54 ?

    dual channel and I think ~$300/~$400

  3. Some two channel J K T H E loggers...
    +/- 0.6 to 1 deg F?

    Maybe you need a silicon bandgap temp sensor?


    That's your best deal there I think, it gives you SD card for recording
    and it has a long data-logging run time.

    That comes with 3 channels with K probes, etc..

  5. miso

    miso Guest

    So how did you temperature test it in the first place?

    I've never cranked a test oven that high. Probably the max I ever did
    was 170 deg C testing thermal shutdown.
  6. The Pico Thermocouple data logger is good and has moree than two channels.
    Comes with software and connects to the PC via USB. About half your budget
    level I should think. Last we used this was with a small experiement that
    was monitoring thermal transfer between two metal components in a high power
    scanning electron microscope. As the experiement started melting one of the
    metal components and the readings were still coming I think your range is
    well within its capabilities.


    Paul E. Bennett IEng MIET.....<email://>
    Forth based HIDECS Consultancy.............<>
    Mob: +44 (0)7811-639972
    Tel: +44 (0)1235-510979
    Going Forth Safely ..... EBA.
  7. Guest

    Omega does a lot of temperature stuff and seems to be reasonable about
    having things in stock. I have used their handheld meters and
    thermocouples before in a portable application (college engineering lab
    stuff) and they worked OK, but the requirements there (+/- 1 C or so,
    single channel) weren't as tight as yours. I also used one of their
    bench-type meters - really an industrial panel meter in a box - with
    thermocouples at work for product testing (+/- 1 C or so, multiple
    channels) and it worked OK.

    Looking at their online catalog... HH501DK. 4 channels, Type K,
    "±(0.3% rdg + 1°C) -50 to 1000°C". No mention of isolation. It even
    comes with four simple Type K thermocouples and a battery, for $125.

    HH147U. 4 channels, Type K plus others, "±(0.1% rdg + 0.7°C) -100 to
    1300°C" for Type K. It will log data to internal memory and download
    it via USB. No mention of isolation. It comes with Windows software,
    one simple Type K thermocouple, and batteries, for $300.

    RDXL4SD. 4 channels, Type K plus others, "-50.1 to -999.9ºC
    ±(0.4% + 1ºC)" for Type K. (I think that's a misprint and should
    really be -50.1 to +999.9 C.) It logs data to an SD card and also
    has a USB connection, but the Windows software is apparently separate
    at $100. No mention of isolation. It comes with a 2 GB SD card, no
    batteries (6 AA) or thermocouples, for $300.

    There are some other models that may fit the bill, including HH1384
    ($375), HH309A ($315), HH374 ($300), and HH378 ($340).

    This may be in the "grandmothers and eggs" category, but one thing I
    have found, with any portable thermocouple application, is that the
    screws inside the thermocouple connectors at the meter end tend to
    loosen up as things are banged around. A lot of meters can tell if the
    thermocouple is completely open circuit, but I have found that they
    can't detect slightly-loose screws that give unstable readings. One
    way I have found this problem is to put the thermocouple junction in a
    place where the temperature should be pretty stable, and then tap and
    tug on the connector with my fingers.

    Standard disclaimers apply: I don't get money or other consideration
    from any companies mentioned.

    Matt Roberds
  8. If you were willing to use RTDs, something like an Adam 6015
    (Advantech) would handle 7 channels, have 10/100 Ethernet interface,
    and fits your price budget. No display, but I think they have free
    software for viewing the readings on a netbook or whatever.

    Accuracy should be considerably better than T/C over that range,
    particularly if the ambient temperature is not closely regulated.

    Best regards,
    Spehro Pefhany
  9. Artem

    Artem Guest

    Any free Modbus/TCP software.

    Or maybe only web browser will be necessary.
  10. None, (sorry) But I'm interested in what others offer.
    One issue I found with a cheap omega (panel mount) was that the cold junction temp sensor seemed to be on the opposite end of the pcb from the TC input.
    I guess not that much of an issue if you mostly care about relative temps and not absolute.
    (I can send a bucketful* of pnp's in to-220 packs that are calibrated to ~0.3C from 77K to 400K.. with most of the uncertainty at the low temp end.) calibration table.doc

    George H.
    * well ok not a bucket full... I have to do a single point room temp measurement on each one...but 2-3 is easy.
  11. RobertMacy

    RobertMacy Guest

    With a thermocouple mounted on the envelope and at that close aproximity,
    wouldn't radiation effects get into play?
  12. Phil Hobbs

    Phil Hobbs Guest

    Sure. What I'm trying to track down is a DC drift problem in a chopped
    AC measurement. One of those effects you don't usually think about too
    much is the effect of ambient temperature on bulb output.

    If you take a tungsten bulb at constant input power, and raise its
    ambient temperature by 10 degrees, the filament will get hotter by
    probably 2 or 3 degrees, so it gets a bit brighter. The thermocouple
    will see both effects, but it'll at least allow me to estimate whether
    they're plausible causes.

    It's a fibre-bundle spectrometer, so there are other possible issues,
    e.g. mechanical drift plus a moire pattern between the fibre ends and
    the image of the helical filament. The particular bulb has a box-wound
    filament, and is canted a few degrees so that the wire in the back of
    the helix fills in the spaces in the front, but there could still be
    some residual effect.

    The first thing you look for in debugging thermal problems in an
    optomechanical system is bending due to temperature gradients or
    dissimilar CTEs.

    My original prototype was built open-style, using Microbench optical
    rails and an RC-airplane servo motor for turning the grating, with a
    CMOS mux as the phase detector and a LabJack U6Pro for data acquisition.
    The new swoopy one has a very nice 3D-printed case, a proper encoder
    on the shaft, and an all-digital back end.

    But it drifts, and mine didn't (despite being made of toy parts and
    dead-bug circuitry). We're going to spend next week going through it in
    the goriest possible detail, because I have no interest whatsoever in
    doing it over again.


    Phil Hobbs

    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
  13. miso

    miso Guest

    Ovens are pretty cheap on the surplus market if you only want heat.
    Cooling takes forever without the nitrogen tank.

    I've had bad luck with refrigerated test chambers as far as reliability
    goes, but much less condensation during cold testing than with that
    nitrogen blaster. I do know someone that swears by Thermotron test
    chambers. Not to be confuser with the old Thermostream by Temptronic,
    AKA the cone of silence chamber.
  14. Fred Abse

    Fred Abse Guest

    Do you have any experience with those? I have a job coming up requiring
    monitoring of multiple temperatures. The Extech looks attractive, and the
    price is right on the money. Thermocouple accuracy is fine.

    I'd appreciate any comments you might have.
  15. I don't have that unit but we have a visiting tech for a specific
    machine that is rented and he swears by it. He has left it at out place
    a couple times to do long data logs.

    I do have some Extech gear myself, one of them has a K-probe and IR
    probe on it. I would not trust the IR probe so much but the K-probe is
    very accurate. That meter has been dropped, bagged around and it still

    I also have an Agilent K-probe meter but at times I question that.

  16. Fred Abse

    Fred Abse Guest

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