Free Engineering Tool
Measurement
Meter Accuracy and Error Band Calculator
A meter spec like ±(0.5% + 3 digits) is not one number. Enter your reading and the spec to see the real band the true value sits in.
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Inputs
On a 600.0 V range the last digit is 0.1. On a 6.000 V range it is 0.001.
Readout
How the spec works
Error = (reading × %) / 100 + (digits × resolution)
Example: 230.4 V on a meter rated ±(0.5% + 3 digits) with a 0.1 V last digit. The percentage part is 1.152 V and the digits part is 0.3 V, so the error is ±1.45 V and the true voltage is between 228.95 V and 231.85 V.
Why it matters
- A fixed "+ digits" term hurts most at low readings. On a high range, a small reading can be mostly error.
- A reading outside the band around an expected value means the circuit, or the meter, is genuinely off. A reading inside it proves nothing more than agreement.
- Accuracy is only valid at the stated temperature, after warm-up, and within a valid calibration interval.
Read the difference between accuracy and resolution in accuracy vs resolution vs precision. When choosing an instrument, see how to choose a multimeter.
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