DampingT1

DampingT1 (FB)

FUNCTION_BLOCK DampingT1

Short description

Temporal filtering of an analog input signal Typical application: filtering of a sensor raw value

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
rIn	REAL			Analog value input

Outputs

Name	Data type	Value range	Initial value	Function
rOut	REAL			Filtered analog value output

Setpoints / parameters

Name	Data type	Value range	Initial value	Function
tTimeConstant	TIME	5s…	T#10s	Filter - time constant
rInitValue	REAL		100	Initial value
eInitial	eInit		eInit.InputValue	Selection of the initial value
tInitDelay	TIME		T#5s	Start delay - initialization

Function description

General

The analog input signal rIn is examined at intervals of the sampling time (here: 1s, fixed) for changes in its value. If the current value at the input rIn at time t differs from the value at the output rOut at time t-sampling time, then the current output value rOut at time t is calculated according to the following algorithm: rOut = rOut (t-sampling time) + ((rIn - rOut (t-sampling time)) * (sampling time / tTimeConstant)) Legend:

1. rOut = filtered analog value output at time t
2. rOut (t-sampling time) = filtered analog value output at time t-sampling time
3. rIn = analog value input at time t
4. Sampling time = 1s
5. tTimeConstant = filter - time constant
6. t = current time

Rules for setting the filter time constant tTimeConstant

tTimeConstant > (sampling time * 5) tTimeConstant = 0: rOut = rIn

Type of initialization eInitial

This setpoint / parameter determines the type of initialization of the analog value input rIn is defined. The initialization is performed once after each CPU restart. The following options are possible:

Type	Initialization value	Note
eInit.InitValue	rInitValue	Configurable initial value
eInit.InputValue	rIn	Input value
eInit.InputValueDelayed	rIn	Delayed input value

The initialization is performed continuously regardless if the setpoint / parameter tTimeConstant has the value T#0s.

CODESYS

InOut:

Scope	Name	Type	Initial
Input	rIn	REAL
Input Const	tTimeConstant	TIME	TIME#10s0ms
Input Const	rInitValue	REAL	100
Input Const	eInitial	eInit	eInit.InputValue
Input Const	tInitDelay	TIME	TIME#5s0ms
Output	rOut	REAL