Difference between QA351 and the $2500 6.5 digit DVM

QA351
1

The $2500 6.5 digit DVM probably has amps, resistance, AC volt with RMS and probably more. But when we cut that and just look at what the QA351 delivers, what does a $2500 6.5 digit DVM do more then the QA351?. One of the strong points in my view is that you can calibrate your QA351 with what’s onboard in the QA351. I didn’t found that in the specs of a $2500 DVM. And calibration is definitely “something” in a diy lab. Or do I have to look elsewhere? I need a source on which I can hook al my calibrations. I think that QA351 can just do that. I don’t need high voltages, +26dBV is about it, if I ever need that, most of the times it will stay at +4dBV.

2

Hi @Joop99, the biggest shortcoming you’ll find in the QA351 vs a benchtop 3.5 digit DVM is the reference. The QA351 uses a MAX6126A reference, which exhibits about 3ppm/C. A benchtop DVM will usually used an “ovenized” reference which runs hot on purpose (far above ambient) and is thus insensitive to temperature changes. Also, note the QA351 doesn’t do AC measurements. It’s just DC.

Thanks, Matt

3

Thank you for your answer. The 3.5 digit is a typo. I have a hard time in finding a 6.5 digit DVM. Let alone the price of $2.500. I took R&S HMC8012 (about half that price, I took R&S as example because its a serious manufacturer, don’t know what to think from some Chinese brands) and did some calculations about accuracy on a measured 2.5V DC. Room temp 23grC. The combined error for the HMC8012 is 0.000875V or 0.0350%, this is anywhere between 2.500875V and 2.499125V.
The QA351 is specified worst case. I refer to MAX6126A with package 8 SO A-grade otherwise we have other problems. Temp coef is typical 0.5ppm/c and max 3ppm//c. I took worst case. The combined error for 2.5V is 0.000565 or 0.0226%, this is anywhere between 2.500565V and 2.499435V. So you can’t calibrate this R&S DVM, but most of my stuff can be calibrated as it doesn’t do better then 0.1%, most of the instruments are somewhere between 1% and 3%. Yes I know that QA351 doesn’t do AC measurements, but my own stuff can be calibrated with DC. I’m busy with an audio oscillator (on batteries), when that’s ready I can do AC.
Regards
Joop