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| DMMCheck Plus Multimeter Reference(and other References) - Experiences.. |
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| DavidKo:
Using the probes is not ideal, you can create the Seebeck effect simply by heating one probe more when holding it. |
| J-R:
--- Quote from: DavidKo on August 04, 2023, 07:15:45 am ---Using the probes is not ideal, you can create the Seebeck effect simply by heating one probe more when holding it. --- End quote --- It's just not really visible on a 6.5 digit DMM @ 5V. Test leads are well insulated, so the metal tip is not going to be heating up much at all, and if it does, once you start holding it against the terminals the temperature differential will be absolutely miniscule. Maybe if you have soldering irons for fingers. For sure the way to easily see this though is to drop into the mV range and heat the probe tips with your fingers directly. Then the effect is immediately visible. Otherwise as I mentioned you mostly start to worry about such things at 7.5 digit DMMs and above. And really one of the top rules at this level is that your hands are in the next room... |
| KungFuJosh:
--- Quote from: DavidKo on August 04, 2023, 07:15:45 am ---Using the probes is not ideal, you can create the Seebeck effect simply by heating one probe more when holding it. --- End quote --- --- Quote from: J-R on August 04, 2023, 07:59:23 am ---And really one of the top rules at this level is that your hands are in the next room... --- End quote --- This is why I saw to use probes with clips/grabbers, so your hands aren't anywhere near the test. |
| J-R:
I experimented and researched a bit more and will still postulate that holding the probes makes no difference in the context we are discussing. The reason this is the case is that you are heating up both probes at the same time, so it cancels out the effect. Furthermore, 5V on most bench DMMs is going to push you up into the next range, so you lose a digit. So even at 7.5 digits, whether you hold the probes or not really makes no difference. I was hard pressed to even see the effect at 1V on my Keithley 2010 when holding one probe tip directly. |
| KungFuJosh:
--- Quote from: J-R on August 04, 2023, 05:58:33 pm ---I experimented and researched a bit more and will still postulate that holding the probes makes no difference in the context we are discussing. --- End quote --- For the sake of heat, you're probably right. However, relying on hands to hold probes in place consistently gives inconsistent results. Grabbers force contact consistency, and you can run the test 100 times without change to the results based on contact changes. |
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