Troubleshooting
7-14
TI545/TI555 System Manual
7.8 Checking RS-485 (Twisted Pair) Cable Installation
To
locate problems with RS-485 communication links, use a digital or analog
meter capable of measuring resistance between 0 and 150 ohms.
Measure the line-to-line and line-to-shield resistance as follows:
1.
Remove power from the controller and all bases.
2.
Disconnect the CPU and all RBCs from the cable by removing the 9-pin
D-connector.
3.
Measure the resistance from either isolated wire to the other isolated
wire (line-to-line) and record this value.
4.
Measure the resistance from one line to the shield wire and record this
value.
5.
Measure the resistance from the other line to the shield wire and
record this value.
6.
Compare the values you recorded with those in T
able 7-3.
T
able 7-3
Cable Resistance
9860 or 9271 9182
Min Max Min Max
Line-to-line 52 ohms 70 ohms 63 ohms 87 ohms
Line-to-shield 100K ohms – 100K ohms –
Using
Digital or
Analog Meter
To Next Page
Loading...
