Siemens SIMATIC User Manual

Principles of analog modules
5.5 Conversion and cycle times of analog modules
S7-300 Module data
290 Manual, 06/2017, A5E00105505-AJ
Example
Two analog input channels of the SM 331; AI 2 x 12 Bit analog input module form a channel
group. You must therefore grade the cycle time in steps of 2.
Setting smoothing of analog values
Certain analog input modules allow you to set smoothing of analog values in STEP 7 .
Using smoothing
Smoothed analog values provide a reliable analog signal for further processing.
It is useful to smooth the analog values with slow variations of measured values, for
example, when measuring temperature.
Smoothing principle
The measured values are smoothed by digital filtering. Smoothing is accomplished by the
module calculating mean values, derived from a defined number of converted (digitized)
analog values.
The user configures up to four grades of smoothing (none, low, average, high). The grade
determines the number of analog signals used for averaging.
A higher smoothing provides a more reliable analog value, and prolongs the time it takes to
apply a smoothed analog signal following a step response (see the example below.)

Siemens SIMATIC Specifications

General

Product type designation	SIMATIC
CPU	Varies by model
Memory	Varies by model
Input/Output	Varies by model
Communication	Varies by model
Programming Language	STEP 7
Operating Temperature	0°C to 60°C (varies by model)
Protection Class	IP20
Category	Programmable Logic Controller (PLC)