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My Evolution



  • I think you could find a thermocouple to do the job for about 1/20 the cost of $55.

    I'm more like I am now than I was before.

  • I find thermocouples to generally have poor accuracy and terrible repeatability. Nonlinearity makes single point calibration impossible, and dealing with extended lead lengths just make everything that much more difficult.

    If getting the correct measurement is important, surely it's important enough to spare the cost of a couple of extra beers on gear that will give you the correct number, not just some number.

    At least that's the way I feel, ymmv.

  • edited February 2015

    I wish I had known that before having such good luck using thermocouples for the last six years. I use them more for trending than 0.1 degree of accuracy. (precision over accuracy)

    The actual numbers on the readout are almost meaningless to me. The slope of the curve is what I look at. Thermocouples read rock steady when hearts are coming off. They move predictably when tails start to come off. Very good repeatability for the price IMHO.

    I'm more like I am now than I was before.

  • Wish I could say the same. I've used both types and feel that the disadvantages of thermocouple vastly outweigh the minor cost savings. The last place I used thermocouple successfully was measuring the exhaust gas temperature of my car's turbocharger, where the TC responsiveness and vast temperature range win out (you can't really measure 1500F with an RTD). However, being off by 20 degrees in this situation is irrelevant, and responsiveness of measurement is even more critical.

    For our work here, with narrow temp ranges and small variations in temp representing huge changes in vapor composition, RTD is the winner.

    I use decent measuring gear, I use the Omega DP41-B and Newport INFT. I've run both thermocouple and RTD side by side, and the RTD wins out every time. Most of my sensors are Class A, but I do have a few 1/3rd DIN. I also have a box full of good quality thermocouples. I also have calibrated lab glass thermos as reference.

    It's all moot if you don't or can't calibrate.

  • @grim, how often are you calibrating your rtds? And are you basing that on number/frequency of use or simply time in service? I have a few auber probes that seemed to drift after only a few weeks, and I am really not looking to recalibrate every use, so just curious if it is a hardware issue or what.

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