How to Calculate Pressure Transmitter Accuracy?

Answer 1

accuracy with only one variable. Accuracy takes into account several different variables, only one of which is non-linearity. In other words, non-linearity alone does not determine a device’s overall accuracy.

These are the five variables a user should consider when determining pressure transmitter accuracy:

Two methods are used to generate the reference line needed to find a pressure transmitter’s non-linearity: the terminal method, also called endpoint method (blue line) and the best fit straight line method (brown line). The linearity is the largest deviation from the reference line to the actual response (red line).

1. Non-linearity

Non-linearity is the largest deviation between the actual response (red curve) and a reference line. There are two common methods for generating this reference line

The terminal method, also called the endpoint method, draws a straight line from the actual zero point to the actual full scale value endpoint. Since this method is based on the characteristic curve’s endpoints, it is a truer representation of a pressure transmitter’s non-linearity.

The best fit straight line (BFSL) method is a straight line that stays within a certain percentage deviation from the characteristic curve, or actual response. The endpoints do not figure into this method. BFSL method values are typically half of terminal method values, meaning that a pressure transmitter with a ±0.25% BFSL non-linearity allows for a ±0.50% error.

Zero offset and span tolerance when calculating pressure transmitter accuracy

2. Zero offset

The zero offset is the deviation between the ideal line’s zero point and the characteristic curve’s zero point (see Fig. 4).

3. Span tolerance

Span tolerance is the deviation of the actual span from the ideal span between the zero point and the full scale point. The span offset is not related to the zero offset and has to be added to it.

4. Hysteresis

Hysteresis is the lag between a change in pressure and the corresponding change in the pressure transmitter signal. It is an indication of how fast or slow a pressure transmitter responds to input changes.

5. Non-repeatability

Non-repeatability is the maximum difference in the signal of the pressure transmitter for the same applied pressure. It is an indication of how much the transmitter duplicates measurements for the same input.