What Does FS Mean When the Pressure Sensor Accuracy is 0.25%FS?

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1. Pressure Sensor Accuracy in WIKA Datasheets

In WIKA datasheets, pressure transmitters are marked with 0.125%FS. What does the suffix FS stand for?Let’s figure out this question together today.

2. Meanings of Full Scale Accuracy and Reading Accuracy

Reading Accuracy: It is an error proportional to the measured value.Full Scale Accuracy: It is an error proportional to the measuring range, a fixed error expression method that refers to the error relative to the full scale of an instrument, expressed as a percentage.FS in WIKA datasheets refers to Full Scale, i.e., the full measuring range!

3. Calculation Examples

Full Scale Accuracy is widely used in pressure testing.Suppose we have two pressure transmitters, both with a measuring range of 100 bar.Let’s compare the differences in calculated error values between Reading Accuracy and Full Scale Accuracy:(1) Reading Accuracy: ±1%System pressure at 10 bar: Measurement error = ±0.1 barSystem pressure at 50 bar: Measurement error = ±0.5 barSystem pressure at 100 bar: Measurement error = ±1 bar(2) Full Scale Accuracy: ±1%System pressure at 10 bar: Measurement error = ±1 barSystem pressure at 50 bar: Measurement error = ±1 barSystem pressure at 100 bar: Measurement error = ±1 barIt is clear from the comparison that for selected products with the same accuracy value, a pressure transmitter whose accuracy is expressed by Reading Accuracy in the datasheet is definitely more accurate than one marked with Full Scale Accuracy.Then why not just buy pressure transmitters with accuracy expressed by Reading Accuracy from now on?But the reality is harsh...

4. Are There Pressure Transmitters with Accuracy Expressed by Reading Accuracy?

The answer is yes!However, it should be noted that no pressure transmitter can maintain consistent accuracy over its entire measuring range.Therefore, even if a selected pressure transmitter has its accuracy expressed by Reading Accuracy, it is subject to certain range limitations.Take a 100 bar pressure transmitter as an example again: its datasheet is marked with 0.01%RD (Reading Accuracy), but this Reading Accuracy is only valid for 10% to 100% of the full scale, namely from 1 MPa to 10 MPa. For the range from 0 to 1 MPa, its accuracy shall be specified separately.