Omega A2400 - Manual (Page 52)

Chapter 8
Troubleshooting
Symptom: RS-232 Module is not responding to commands
1 Using a voltmeter, measure the power supply voltage at the +Vs and
GND terminals to verify the power supply voltage is between +10 and
+30Vdc.
2 Verify using an ohmmeter that there are no breaks in the communica-
tions data lines.
3 Connect the module to the host computer and power-up each device
(module and computer) then using a voltmeter measure the voltage be-
tween RECEIVE and GND. This voltage should be approximately - 10Vdc.
Repeat the measurement between TRANSMIT and GND terminals and
confirm the voltage value to be approximately -10Vdc. If either of the two
readings is approximately 0.0Vdc then the communications data lines are
wired backwards. Proper communications levels on both TRANSMIT and
RECEIVE terminals should idle at -10Vdc.
4 If you are using a serial communications converter (A1000) ensure that
the communications Baud Rate switch is set to the proper Baud Rate value.
5 Confirm software communications settings in Host computer match
those values being used by the connected module(s).
6 If the Baud Rate value being used in the application is greater than 300
Baud and the module will only communicate 300 Baud then make sure that
the DEFAULT* terminal is not connected to Ground (GND).
7 If the module(s) are being used in a RS-232 daisy-chain communica-
tions configuration then ensure that the “Echo Bit” is enabled in the
setup(SU) message of each module.
8 If the problem is not corrected after completing the steps above then
connect the module by itself to a Host computer as outlined in Chapter 1.0
under “Quick Hook-up”. Start the supplied Utility software and please call the
factory for further assistance.
Symptom: RS-485 Module is not responding to commands
1 Perform steps 1, 2, 4, 5 and 6 listed above.