What happens?
The analogue actual value of analogue I/O1000 modules connected to the CANopen bus coupler EPM-S110 assumes a very large positive value instead of a negative value (>65000) - actual value jump.
When does the behaviour occur?
The channels of the I/O1000 modules EPM-S400, EPM-S401, EPM-S402, EPM-S403 and EPM-S408 on the CANopen bus coupler EPM-S110 have the data type WORD. This means that the process variables declared in the I/O mapping of the I/O module also have this data type. If the value at the analogue terminal becomes negative, this leads to a very high positive value of the process variable.
Which products are affected?
PLC Designer V3.0
CANopen Bus Coupler EPM-S110 with analogue input modules EPM-S400, EPM-S401, EPM-S402, EPM-S403 and EPM-S408.
Short-term measures:
Convert the data type of the process variables from WORD to INT. A simple way to do this is to declare a global variable of type INT and assign it to the channel in the I/O mapping of the module.
In addition, limit the value range of the variable to values between 0 and 16384.
Evaluation:
The value range of the analogue I/O1000 input modules mentioned above is between 0 and 16384 by factory setting. Nevertheless, the modules can measure a very small negative value and transmit it to the controller. Due to the preset data type of the analogue channels in the PLC Designer, the evaluated actual value can assume a very large positive value instead of a negative value and thus lead to misinterpretation in the PLC logic. An applicative solution is described under 'Short-term measures'.
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