Accuracy Specification Calculator
Instrument and calibrator specifications often mix percent of reading and percent of full scale. Work out the allowable error at any point and compare the two styles.
- Error = 0.05 % × 25 + 0.02 % × 100 = ± 0.0325
Error across the range
| Reading | Error | % of reading |
|---|---|---|
| 10 | ± 0.025 | ± 0.25 % |
| 25 | ± 0.0325 | ± 0.13 % |
| 50 | ± 0.045 | ± 0.09 % |
| 75 | ± 0.0575 | ± 0.07667 % |
| 100 | ± 0.07 | ± 0.07 % |
Combined Accuracy Specification
Worked example
A calibrator rated ± (0.05 % of reading + 0.02 % of FS) on a 100 bar range: at 25 bar the error is 0.0125 + 0.02 = ± 0.0325 bar, or 0.13 % of reading.
Frequently Asked Questions
What is the difference between % of reading and % of full scale?
% of reading scales with the value measured; % of full scale is a fixed error in units across the whole range.
Why do specs combine both terms?
Gain errors scale with reading while offset and noise do not; the two terms describe both.
How should I compare two calibrators?
Calculate the error of each at the readings you will use most, including any temperature and stability terms.
Learn more on the blog
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