If Voltages Are Too Low - Parker H Series Installation & Service Instructions Manual

Table 5.2 Nominal DeviceNet voltage readings
Table 5.2 lists nominal voltage readings.
Because the differential voltages are constantly shifting
TIP
among the three wires, the voltages on your scope trace
may differ from the nominal voltages shown in Table 5.2.
These voltages assume no common mode effect on the V-
and are for reference only.
when a network master
is not connected to the network
is connected to, and is polling
the network

If voltages are too low

If the CAN_H to V- and CAN_L to V- voltages are too low (less than 2.5V dc
and 2.0V dc, respectively), the transceiver or wiring may be bad.
To check the transceiver for proper operation:
1. Remove one DeviceNet node from the network.
2. Use an ohmmeter to check for resistance greater than 1MΩ between:
• V+ and CAN_HI
• V+ and CAN_LO
• V- and CAN_HI
• V- and CAN_LO
Correct and Prevent Network Problems
CAN_H to V- voltage
should read
between 2.5 - 3.0V dc
approximately 3.2V dc
Publication DNET-UM072C-EN-P - July 2004
5-9
CAN_L to V- voltage
should read
between 2.5 - 3.0V dc
approximately 2.4V dc