When designing a new system or device, there are enough problems to solve without worrying about the reliability of pressure transducers. Choosing a sensor with a low total error band can make designing the system easier.
What is Total Error Band?
Total Error Band (TEB) is the most comprehensive measurement of a sensor's actual accuracy over a compensated temperature range. In other words, it is a measurement of worst case error. TEB is valuable when determining whether or not a sensor will work within a particular system as it includes more factors than just accuracy.
Factors of Total Error Band
In all, five elements go into calculating TEB for pressure transducers. These elements are accuracy, zero offset, span offset, zero temperature offset, and span temperature offset.
Accuracy
Accuracy is determined by three measurements: non-linearity, non-repeatability, and hysteresis.
- Non-linearity is the maximum deviation of any calibration point on a specified straight line during any one calibration cycle and can be determined one of three ways:
- Best Fit Straight Line (BFSL) Method - relationship of a calibration curve to a specified straight line
- End Point Method - relationship of a calibration curve to a specified straight line through its end points
- Terminal Method - relationship of a calibration curve to a specified straight line with end points at zero and full scale
- Non-repeatability is the ability of a transducer to reproduce output readings when the same pressure value is applied to it consecutively, under the same conditions, and from the same direction.
- Hysteresis is the maximum difference in output at any pressure value within the specified range when the value is approached first when increasing and then decreasing pressure.
Zero Offset
The zero output is factory set to within a certain % of full scale. It results in a shift up or down of the calibration curve and does not affect linearity of accuracy.
Span Offset
The span output is factory set to within a certain % of full scale that results in a charge in the slope of the curve. It does not affect linearity or accuracy.
Zero Temperature Offset
Zero temperature offset is the change in the zero offset due to temperature changes.
Span Temperature Offset
Span temperature offset is the change in the span offset due to temperature changes.
Setra's Model AXD
Setra's Model AXD offers a 1.5% TEB specification over a temperature range of -20 C to 80 C. This specification provides a more comprehensive look at the sensor's performance in real world installations.
