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The absolute value of the threshold value is calculated as follows:
● "Limit value" + "Amount of difference" ("function" = positive)
or
● "Limit value" - "Amount of difference" ("function" = negative)
Block functions
The two functions of the block depend on the position of the threshold value compared with
the Limit value:
● Window (range monitoring)
"Function" = "+ (window)"
Limit value < Input signal < Threshold value
A range of the analog value (window) between limit value and threshold value is
monitored.
Two applications are possible:
– Output = 1, when input signal is within the window.
– Output = 0, when input signal is outside the window.
● Limit value with hysteresis
"Function" = "+ (hysteresis)"
Threshold value < Limit value
The limit value is given a hysteresis for example to control a pump.
Two applications are possible:
– Limit value
– Limit value
Parameters
Parameters
Input parameters
En
RTU3030C
Operating Instructions, 09/2017, C79000-G8976-C382-04
For the operating diagram see Limit value switch.
For this functionality you need to invert the "Output" using the black contact symbol.
with negative hysteresis
high
When the input signal exceeds the limit value the output is set to 1.
When the input signal falls below the threshold value the output is set to 0.
with positive hysteresis
low
You can monitor the input signal for a limit value
invert the input signal (x) using the black contact symbol (1/x).
Tag type / range of
values
5.7 Blocks for analog value functions
with positive hysteresis if you
low
Description
Enable parameter, see section Often used parame-
ters (Page 198).
Programming
223
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