Products > Test Equipment
DMMCheck Plus Multimeter Reference(and other References) - Experiences..
Martin72:
While I will probably repeat my series of measurements....
In the Siglent SDM thread, one criticized that I had contacted the test points on the DMMCheck with probe tips.
Better would be, at least for the voltage / current measurement, to solder shielded wires to the test points and connect the multimeters.
For fun I had done that yesterday and just quickly connected a multimeter - Hmmm...That is actually a difference,
And that's why it will probably be repeated.
J-R:
I disagree with the idea of soldering anything to the reference. The first issue would be heat into the PCB from soldering impacting the reference output, and the second would be simply invalidating the current calibration. So naturally there would be a high probability of a difference in the readings after performing this procedure.
Currently I have 5 calibrated voltage references and two calibrated 6.5 digit DMMs and I have not observed any issues whatsoever from my choice of probe or connection. The only major factor impacting measurements has been time since power on and ambient temperature.
Only with my 7.5 digit DMM am I able to start to begin to observe some of the effects that you have to pay close attention to in the area of metrology, of which I admit I only lightly dabble.
KungFuJosh:
I agree, modifying the reference doesn't make sense to me. I would use good quality probes with clips. If possible, I'd use the same probes and clips with every meter you're comparing.
J-R:
To clarify, even the quality of the probes and clips really doesn't matter at this level.
Consider a 5V reference connected to a 10M Ohm input DMM. Current flow is 0.000,5mA. Add 10 Ohms to that circuit to represent a very bad connection and the voltage drop is only 0.005mV. So you would need a 5 million count or better DMM to even see this (typically a 7.5 digit DMM). If your DMM has a > gig Ohm input option at this voltage, then it truly doesn't matter.
Consider a 1mA current source from the DMMCheck Plus, which in my sample maxes out just above 500mV. The resistance in the circuit would have to exceed 500 Ohms before it would not be able to generate 1mA. Common DMM shunt resistances are around 2 Ohms for mA and 100 Ohms for uA. Again in this case, adding 10 Ohms for a bad connection will not make any difference.
Martin72:
--- Quote --- The first issue would be heat into the PCB from soldering impacting the reference output
--- End quote ---
You shouldn't fry it for minutes, that's right. ;)
But I know that too, accordingly short it happened.
We will see, if the values have become worse, it was due to the soldering. ;)
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