# Calculating measurement errors

Discussion in 'General Electronics Discussion' started by istvanb, Dec 10, 2012.

1. ### istvanb

18
0
Dec 10, 2012
Hi,

Imagine the following scenario:
- I'd like to measure resistance by dividing measured voltage and current
- the voltmeter measuring the voltage has a 1% accuracy
- the hall sensor used for current measurement has 2% accuracy
- the voltmeter which measures the signal from the hall sensor has 5% accuracy

Lets say the real values are:
V=10V
I=1A
therefore R=10 Ohms

Because of the uncertainties above I pretty much will never measure 10 Ohms. I'd like to know what is the MAXIMUM error can be produced by the setup above.

The scenario is an example, because I'd really like to understand the thought process behind the calculated value. I believe that by playing with the numbers I will be able to figure out the proper answer, but I really miss the proper approach. Also playing around with the numbers are not feasible when I do more complex measurement.

I really appreachiate any help here!
thanks.

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,852
Jan 21, 2010
The obvious way to figure this out is to pick values that are +/- 1% in voltage, +/- 2% in current, and +/- 5% in the next stage of current measurement and then determine the actual spread.

Me, I'd just do 1.01 x 1.02 x 1.05 and see what I got.  