As well as limiting the physical values of a channel, you can monitor the signals used by the channel and their limits. You can also enter a predefined error value to be processed by the HMI in the event of an error.
| Master-ID |
Valid range (raw values |
| CAN |
320 to 2120 |
| FSC-IO |
360 to 2040 |
To activate this monitoring, the "Range error" field must be set to ON. The value that the channel is to use if the input signal exceeds or drops below the limits can then be adjusted in the "Error value" field.
Example
Furnace pressure controller
The error value can be adjusted so that the controller sets the controller output in a predefined direction if an error occurs (for example, wire breakage in the input signal of the furnace pressure controller). In this case, the signal would be < 4 mA, which would cause the controller to close the flue gas damper. To prevent this, the error value would have to be defined at the upper value (20 mbar) so that the controller would open the flue gas damper so that sufficient air would therefore be present.
On the HMI, the status indicator "R" (=Range) appears on the top right of the configuration page for analog channels. R indicates a violation of the signal limits:
Green: Signal limits are not exceeded
Red: Signal limits are exceeded