Accuracy Test

[CalTeK]

Hello: I have a test problem!!! A digital voltmeter can display counts up to 1999999 (6 1/2 digits). The range is set to 1 volt and has an input of .724 DCV. With an accuracy specified as +/- (4 ppm rdg + 10 LSD), the accuracy is +/- ____ DCV.

[Dr. Frank]

Hello,
to calculate the error budget is quite easy.

First, you have a 2V range, i.e. up to 1.999 999V display, and its resolution is 1µV.
10 digits (LSD) are therefore 10µV.

4ppm of a 724mV reading are 2.9µV, so the total error would be +/- 12.9µV. (I don't like the term 'accuracy')
That is equivalent to about 18ppm error of you measurement.

So what's your test problem, now?

Frank

[CalTeK]

Thank's Frank. That's what I got.   

[mendip_discovery]

If you want to take it a step further then you need to look at measurement uncertainty which takes into account more of the measurement errors and the uncertainty of the lab that calibrated your 6.5digit meter.

A quick bash into my calculator and I get around 5 μV/V + 13 μV Measurement Uncertainty with a 95% where k=2. But that is using the imported UoM from the lab that did my 6.5digit meter.