Rs-485 communications – WattMaster WM-WCC3-TGD-01B User Manual
Page 464
10. RS-485 COMMUNICATIONS
WCC III Technical Guide
10-12
SAT 3C/D/F Troubleshooting with a Digital Voltmeter
Figure 10-13: Typical SAT 3C/D/F TUC RS-485 Satellite Communications DC Voltage Measurements with the
TUC COMM Loop Connected
Figure 10-14: Typical SAT 3C/D/F TUC RS-485 Satellite Communications DC Voltage Measurements with the
TUC COMM Loop Disconnected
The voltage measurements in Figure 10-13 are approximate voltages. These voltage measurements are taken when the power to the SAT
3C/D/F Controller is “ON” and the RS-485 TUC EXP communications loop is connected. These two voltages will fl uctuate slightly and
also will momentarily “fl ip” to the other meter reading’s value. The voltage measurement from “T” to “SHIELD” should be around 2.7
VDC. The voltage measurement from “R” to “SHIELD” should be around 3.00 VDC. Typical bad voltage measurement values would
be anything above 3.8 VDC and anything below 1.5 VDC. Helpful hint: Removal of the SAT 3C/D/F cover may aid in measuring the
communication loop voltages.
The voltage measurements in Figure 10-14 are approximate voltages. These voltage measurements are taken when the power to the SAT
3C/D/F Controller is “ON” and the RS-485 TUC EXP communications loop is disconnected. These two voltages will not fl uctuate. The
voltage measurement from “T” to “SHIELD” should be around 3.25 VDC. The voltage measurement from “R” to “SHIELD” should be
around 3.25 VDC. Typical bad voltage measurement values would be anything above 3.8 VDC and anything below 1.5 VDC. Helpful hint:
Removal of the SAT 3C/D/F cover may aid in measuring the communication loop voltages.