Process Value Settings V1 - Siemens SIMATIC S7-1200 Function Manual

5.3.1.2

Process value settings V1

Configure the scaling of your process value and specify the process value absolute limits In
the "Process value settings" configuration window.
Scaling the process value
If you have configured the use of Input_PER in the basic settings, you will need to convert
the value of the analog input into the physical quantity of the process value. The current
configuration will be displayed in the Input_PER display.
Input_PER will be scaled using a low and high value pair if the process value is directly
proportional to the value of the analog input.
1. Enter the low pair of values in the "Scaled low process value" and "Low" input fields.
2. Enter the high pair of values in the "Scaled high process value" and "High" input boxes.
Default settings for the value pairs are saved in the hardware configuration. Proceed as
follows to use the value pairs from the hardware configuration:
1. Select the instruction PID_3Step in the programming editor.
2. Connect Input_PER to an analog input in the basic settings.
3. Click on the "Automatic setting" button in the process value settings.
The existing values will be overwritten with the values from the hardware configuration.
Monitoring process value
Specify the absolute high and low limit of the process value. You must enter reasonable
limits for your controlled system. Reasonable limits are important during optimization to
obtain optimal PID parameters. The default for the "High limit process value" is 120 %. At the
I/O input, the process value can be a maximum of 18% higher than the standard range
(overrange). This setting ensures that an error is no longer signaled due to a violation of the
"Process value high limit". Only a wire-break and a short-circuit are recognized and
PID_3Step reacts according to the configured reaction to error.
NOTICE
Your system may be damaged.
If you set very high process value limits (for example -3.4*10
monitoring will be disabled. Your system may then be damaged if an error occurs. You
need to configure useful process value limits for your controlled system.
PID control
Function Manual, 03/2017, A5E35300227-AC
Using PID_3Step
5.3 PID_3Step V1
...+3.4*10 ), process value
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