WattMaster WCC III part 10 - Manual (Page 12)

10. RS-485 COMMUNICATIONS
WCC III Technical Guide 10-10
SAT III Troubleshooting with a Digital Voltmeter
SAT III Communications Troubleshooting with a Digital Voltmeter
The voltage measurements in Figure 10-9 are approximate voltages. These voltage measurements are taken when the power to the SAT
III Controller is “ON” and the RS-485 SAT 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 III cover may aid in measuring the communication loop
voltages.
Figure 10-9: Typical SAT III RS-485 Satellite Communications DC Voltage Measurements with the Loop
Connected
Figure 10-10: Typical SAT III RS-485 Satellite Communications DC Voltage Measurements with the Loop
Disconnected
The voltage measurements in Figure 10-10 are approximate voltages. These voltage measurements are taken when the power to the SAT
III Controller is “ON” and the RS-485 SAT 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 III cover may aid in measuring the communication loop voltages.