Technote #7 - What does the "OPEN WIRE" banner mean on the PLC Tools SIM-ALP2
The "OPEN WIRE" banner on the SIM-ALP2 means that it cannot drive the desired mA signal through the circuit connected to it.
To verify the issue is with the circuit connected to analog simulator, remove the circuit from the red and black post and momentarily install a jumper wire between the red and black post in place of the analog circuit to verify the SIM-ALP2 is functioning properly.
ADVICE FOR TROUBLESHOOTING YOUR ANALOG CIRCUIT. Below are the most common external causes we discover for the open wire banner.
1. User wishes to verify the SIM-ALP2 is outputting the proper mA signal and connects a voltmeter/ampmeter/multimeter in the circuit. The meter either has a blown fuse or does not have the leads in the proper position for checking mA. PLEASE NOTE, a multimeter will measure voltage fine with its fuse blown. It only affects reading amperage circuits. See our article on How to measure a 4-20mA signal without blowing the fuse in your voltmeter
2. SIM-ALP2 is connected to a circuit that requires a Current Source output but use is using Current 2 Wire.
3. User is using the SIM-ALP2 in Current 2 wire mode but has the simulator connected backwards. In Current 2 Wire mode the +24VDC goes to the black terminal and the PLC input goes to the red terminal.