Table of Contents
Advertisement
Hardware Installation Guidelines
3.2
Ground Potential Difference Checks Before Connecting
Before a device can be connected to the RS-485 communication line, it must be checked for ground fault.
Uncorrected ground fault can damage all devices connected to the RS-485 communication line.
To check if there is ground fault for a new unit, follow the steps below.
1.
Apply power to all devices already successfully connected to the RS-485 line.
2.
Power up the new unit, but DO NOT connect it to the RS-485 line.
3.
Connect the signal ground (SG) of the RS-485 line through a 10K limiting resistor.
4.
Measure the AC and DC voltage across the resistor. There should NOT be more than 1 volt across the
resistor. Otherwise find and clear the fault.
5.
Connect the new unit to the RS-485 line if no ground fault is found.
44 —
revision 7
Advertisement
Table of Contents
