5-7
5
Wrong Modbus
Query the 4899A's Modbus
address or address
device address and compare it
changed.
against Modbus device setting.
Set Modbus device address
with the C n command.
Message not being
Watch Access LED on
received by the
Modbus device to verify
Modbus device.
serial message received by
Modbus device.
Command syntax
Modbus device manual for
applicable commands,
registers and values.
Check Modbus Error register
for Modbus problems
Faulty or missing
Modbus timeout
Check Modbus Error Register
Modbus responses
setting
with the E? query for a time
out error (Error 101)
Use D command to lengthen
timeout to 300 or 500 msec.
Save setting with the *SAV 0
command.
No communication on RS-485 not enabled 4899A/4809A RS-485 not
RS-485 link.
enabled.
Check setting with the
SYST:COMM:SER:RS485?
query.
Bad RS-485 data
No termination
Missing pullup or pulldown
on RS-485 link.
resistors. Add resistors to RS-
485 network.
TABLE 5-2 TROUBLESHOOTING GUIDE
CONTINUED
Possible
Symptom
Fault
Action or Check
Содержание 4809A
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