Determining the Linearity Error of a Pressure Transducer

This type of error refers to the straightness of all points measured over the full range of the pressure transducer.  It is some times quoted as an alternative to accuracy, but is mostly incorporated into an overall accuracy with other parameters such as hysteresis and repeatability.

To calculate the linearity of a pressure transducer, first you must collect the measurement data.  The typical way to do this is to apply pressure at fixed intervals from zero to full scale pressure and measure the output at each pressure set-point.  The more pressure points there are, the more accurate will be the linearity calculation.  The minimum number of points to determine linearity is 3 points and there is no limit on the maximum, but 5-10 points is typical for one set of pressure points.

Hysteresis Error Calculation for a Pressure Transducer

This relates to the mechanical hysteresis of the sensing diaphragm where the electrical signal output varies depending on whether the pressure has been increasing or decreasing prior to the measurement.

The way that a pressure transducer is checked for hysteresis is to apply pressure from zero to full scale pressure, typically stopping without overshoot at 5 equally spaced steps in pressure to measure the value. Then repeat the procedure in the opposite direction from full scale to zero pressure.