Calibration Uncertainty for average results when digital meter used for readings

[JohnayG]

Hello,

I am trying to work out the total uncertainty for a measurement, so am using the square root of the reading uncertainty squared + calibration uncertainty squared + random uncertainty squared equation.

I have found in a textbook of mine that the calibration uncertainty for a digital meter (which i used to measure all my results for voltage) is plus or minus 0.5% of the reading + 1 in the least significant digit. Now i have made up tables with all my results for V already, but does this mean i have to put in a calibration uncertainty for every single measurement made; i.e. V at 10ms, V at 30ms etc? And also how would i work out a value to use for the whole calibration uncertainty to use in the equation?

Thanks very much for your time

 

[jbsteele]

.The calibration uncertainty of 0.5% of the reading + 1 in the least significant digit means that for each measurement you make, you must calculate a separate calibration uncertainty and add it to the square root of the sum of the reading uncertainty and random uncertainty squared. To calculate the calibration uncertainty for each measurement, you need to first convert the 0.5% of the reading into an actual value. To do this, you can use the following formula: 0.005 * reading = calibration uncertainty. For example, if your reading was 10V, then your calibration uncertainty would be 0.05V. Then, you would add 1 to the least significant digit to get your total calibration uncertainty. In this case, it would be 0.06V. Once you have calculated the calibration uncertainty for each measurement, you can add them into the equation to get the total uncertainty. I hope this helps!