Siemens S7-300 Input filters software filter, Principle of interference suppression with Step

Technical data of CPU 31xC

6.6 Technical data of the integrated I/O

Input filters (software filter)

The current / voltage inputs have a software filter for the input signals which can be programmed with STEP 7. It filters the configured interference frequency (50/60 Hz) and multiples thereof.

The selected interference suppression also determines the integration time.

At an interference suppression of 50 Hz the software filter forms the average based on the last 20 measurements and saves the result as a measurement value.

You can suppress interference frequencies (50 Hz or 60 Hz) according to the parameters set in STEP 7. A setting of 400 Hz will not suppress interference.

An integrated low-pass filter attenuates analog input signals of channel 0 to 3.

Selection in STEP 7

(Software filter)

A/D converter

AIx

50-Hz configuration (mean value filter)

60-Hz configuration (mean value filter)

400-Hz configuration

Hardware low-pass filter

(RC circuit)

Figure 6-4 Principle of interference suppression with STEP 7

6-36	CPU 31xC and CPU 31x, Technical data
	Manual, Edition 08/2004, A5E00105475-05