Yes, you can use as many Inputs as you would like to create a redundant system so your PID controller or other Functions don’t stop working if one or more Inputs fail. To do this, follow the below instructions:
- Add and activate all your Inputs. For this example, we will use three temperature sensors, Sensor1, Sensor2, and Sensor3, that return measurements in degrees Celsius.
- Go to the Setup → Function page and add the Redundancy Function.
- In the options of the Redundancy Function, set the Period, Start Offset, and Max Age, then select Sensors 1, 2, and 3 for Measurements A, B, and C, receptively, then Save.
- For this example, we are using the order Sensor1, Sensor2, Sensor3, but you can specify whichever order you want to use.
- In the options of the Redundancy Function, under Measurement Settings, select Celsius for the Measurement Unit and click the Save under Measurement Settings (a different Save button from the general options).
- Activate the Redundancy Function.
- Go to the Data → Live page and verify the Redundancy Function is working correctly by returning a value from the Input you selected to be first. If the first Input is working correctly, its value should be displayed. You can deactivate the first Input (mimicking the first Input stopped working) and see if the second Input’s value is then returned.
- Go to the Setup → Function page and change your Function or PID controller’s Measurement option to the new Redundancy Function’s measurement.
The Function or PID controller will now use the measurement returned from the Redundancy Function, which in turn will acquire its measurement in the following way:
If a measurement can be found within the Max Age for Sensor1, the measurement for Sensor1 will be returned. If a measurement from Sensor1 can not be acquired, and if a measurement can be found within the Max Age for Sensor2, the measurement for Sensor2 will be returned. If neither a measurement from Sensor1 nor from Sensor2 can be acquired, and if a measurement can be found within the Max Age for Sensor3, the measurement for Sensor3 will be returned. If neither a measurement from Sensor1, Sensor2, nor Sensor3 can be acquired, then the Redundancy Function will not return a measurement at all (indicating all three Inputs are not working). It is recommended to set up a Conditional Controller to send a notification email to yourself if one or more measurements are unable to be acquired so you can investigate the issue.