Application note

Analogue Input Filter

All analogue input channels (PD 640, PD 641, PD 642 and PD 643) have an integrated filter to remove the influence of 50Hz and 60Hz noise.

For further filtering, a filter can be activated with a time constant from 3 to 50 seconds.
This filter can be used to reduce fluctuations in the process signal. This could, for example, be due to disturbance in the contents of a tank caused by an agitator.

The filter constant defines that for a step change at the input terminals, the AnalogIn signal will have changed by 63% of the step process value after the period of the filter constant.

For every “FilterConstant” time period the signal will grow 63% closer to the target value. Target value is the AnalogIn signal calculated directly from the input signal.

(See also: FilterConstant.)


Related Topics

Pt100 / Pt1000 Offset adjustment
Transmitter error compensation
Application note for PD 640 (mA)
Application note for PD 641 / 643 (Pt100 / Pt 1000)
Application note for PD 642 / 643 (mV / thermocouple)
Analogue modules