DMM Accuracy Spec- How to Interpret?
DMM Accuracy Spec- How to Interpret?
(OP)
How does one interpret the accuracy specification on a DMM.
In this case a 3 1/2 digit LCD display, 2000 count meter.
For example, under DC volts the following is shown for the 20 Volt Range:
+/- 0.8% of reading + 5 digits.
Range: 20.00V
Resolution: 10mV
Using a 10 VDC reading (as an example), I can see where +/-.8% of reading indicates that the meter can display anywhere between 9.92 -10.08VDC. How does one interpret the + 5 digits?
Thank you
In this case a 3 1/2 digit LCD display, 2000 count meter.
For example, under DC volts the following is shown for the 20 Volt Range:
+/- 0.8% of reading + 5 digits.
Range: 20.00V
Resolution: 10mV
Using a 10 VDC reading (as an example), I can see where +/-.8% of reading indicates that the meter can display anywhere between 9.92 -10.08VDC. How does one interpret the + 5 digits?
Thank you





RE: DMM Accuracy Spec- How to Interpret?
In modern terminology I should be saying "uncertainty" rather than "error"
You are nearly there with your 10V example. The meter might read 10.00V. ±0.8% is ±8 digits and then you have another ±5 digits. Result ±13 digits. The "digits" refer to the least significant digit position of course.
10.00V ± 0.13V.
RE: DMM Accuracy Spec- How to Interpret?
Or, in a different example, say the actual measured voltage is an automobile battery at 12.60VDC. The meter could display a reading anywhere from between 12.45 to 12.75VDC?
12.60V x .8% =.10 (12.6-.10) = 12.50
12.50-(5 digits)= 12.45
12.60V x .8% =.10 (12.6 +.10)= 12.70
12.70+(5 digits)= 12.75
Is this correct?
Thanks again
RE: DMM Accuracy Spec- How to Interpret?
This maths looks a bit dodgy though ...
12.60V x .8% =.10 (12.6-.10) = 12.50
Looks like a cut and paste error.
I would have gone
12.60 + 0.8% = 12.6*(1.008) = 12.70
12.60 - 0.8% = 12.6*(0.992) = 12.50
RE: DMM Accuracy Spec- How to Interpret?
http:
and select the note for "Understanding DMM Specifications", does a great job explaining accuracy and uncertainty specifications.
We use a lot of these notes for technician training, as the info is pretty general in nature and most times applies to other makes of DMM's.
Hope that helps.
RE: DMM Accuracy Spec- How to Interpret?