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| Reference PCB for Calibrating DMM's |
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| JenniferG:
I ran across this on Amazon for under $13: https://www.amazon.com/Viupolsor-Reference-Resistor-Calibration-Multimeters/dp/B0BKPHPHZQ If I bought this, I am wondering if I could take it to my local electronics store and have them (or pay them) to record the results for voltage and resistances onto the pcb. Or perhaps someone here sells those boards with values they recorded from a very good calibrated meter? I just need a reference to see which of my meters is off.. the 8251A or the UT61E. I want to see how close both are to actual values. I also need a reference in case I need to calibrate a meter. |
| coromonadalix:
as you wrote they are mostly fine BUT you need them properly certified with the voltages "read values" written on them, some peoples check them with 3458 meters, with proper warm up times etc ... Since there is no value markings i would still have doubts .... you have lm399 or ltz 1000 projects here on eevblog (but costly) |
| dophuc:
You should buy a referenced circuit board with a value on it Examples of similar products from Aliexpress https://www.aliexpress.com/item/1005002270593558.html?spm=a2g0o.order_list.0.0.21ef1802t7vwu4 |
| Kleinstein:
Similar boards are offered in number variants. Many of them come with written values for the actual values, e.g. measured with a good quality meter. While many of those reading are legit, there also cases with just arbitrary numbers >:D. For the AD584 reference there is no need for a 8 digit meter - a proper calibrated 34401 would be good enough. Even the recycled reference chips can initially show quite some drift. These boxes are OK for a simple check of handhelp meters. They don't replace a proper calibration if required. A point is a lack of reliabilty, like the small the chance to have fake numbers writen on them. With the relatively high resolution 8251A one may be able to check the ratio and this way has a good chance to detect more random fake values. The boxes would mainly check 1 of the voltage range and maybe the resistors. Even without good values to start with one can still check for excessive drift and use it as a stable source to compare 2 meters. For the shown PCB from amazon the somewhat special battery type could be a slight weak point. |
| robert.rozee:
--- Quote from: JenniferG on November 24, 2022, 11:34:16 am ---I just need a reference to see which of my meters is off.. the 8251A or the UT61E. I want to see how close both are to actual values. I also need a reference in case I need to calibrate a meter. --- End quote --- your GW Instek GDM-8251A is a 5½ digit multimeter, with a DC voltage accuracy of 0.012%. assuming it has not suffered some major mishap in the past, i would consider it far more likely to be reading accurately than the UT61E :-+ initially, you might like to buy something like a MAX6350 reference IC, which is available with an initial factory calibration to within +/-0.02%. for an example see: https://geoffg.net/Voltage_Reference.html showing just the single DIP IC placed in a box, you can't get much simpler. the MAX6350's 5v output sits near the middle of the range of your 8251A, which is probably a good choice of calibration point. cost: around us$20. you can also pick up a 10k 0.01% resistor for less than us$10 (both prices from digikey, farnell will no doubt have similar). this will provide you with some certainty of your meter's performance on DC volts and ohms. cheers, rob :-) |
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