The response time behaviour of pressure sensors: How may be the response time defined and what’s this is of the rise time?

The response time of pressure sensors is reflected in a large number of varying parameters, such as the response time, settling time or rise time in specifications or data sheets. In general, it can be assumed that the response time means the interval required by the output signal of a pressure sensor to display a big change in the applied pressure. Of greatest practical relevance may be the so-called rise time. The graphic shows a simplified diagram of a steplike change in pressure (shown in blue) with a time-delayed change in signal of the pressure sensor (shown in red). With regard to simplicity, the picture only shows a perfect situation.
The truth is, the response time of pressure sensors contains further influencing factors, such as dead time or overshoot, due to their particular constructive setups. Common data sheet specifications on the response time usually contain additional data concerning the test conditions applied, such as for example T90 or 10 ? 90% (used below for exemplary calculation). This information defines the interval in which a steplike change in the applied pressure from 10 to 90% of the full span (e.g. from 60 to 540 bar for a 0 ? 600 bar pressure sensor) results in a defined change in output signal of 10 to 90% of the ultimate value (e.g. from 1 to 9 V at an output signal of 0?10 V).
The standard design of modern pressure transmitters already allows rise times of ? 2 ms. However, pressure gauge (such as submersible pressure transmitters) may also show clearly higher values of ? 100 ms deliberately. The basic rule is that in applications with high load cycles, such as in mobile hydraulics, short rise times are recommended, whereas in slow applications, such as level measurements by submersible pressure transmitters, long rise times are often advantageous.

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