YSI 6500 Environmental Process Monitor - Manual (Page 61)

Troubleshooting Section 6
6.6 4-20 MA CURRENT LOOP OUTPUT PROBLEMS
Symptom: 4-20 mA output values at the SCADA or recorder are
suspicious or inconsistent with the scale you have set in the 6500 setup
menu.
Possible Cause and Suggested Action: The problem may be related to the 6500 circuitry, the wiring
and/or the SCADA controller. Use the diagnostics menu in the 6500 Monitor to check the outputs of
the 4-20 mA outputs. Start checking at the SCADA and work back to the 6500 Monitor. By starting
with the SCADA input you may avoid the need to remove the front cover of the 6500 Monitor, which
is often installed outside.
Activate the Main menu of the 6500 by pressing the Esc and Enter keys simultaneously for 1 second.
Highlight the “4-20 mA” selection and then the “Test 4-20” selection. An example display is shown
below. The values shown should be the current 4-20 values for each of the active current loops.
Using an ammeter verify that these readings are the same as those at the input of the SCADA
controller. If they do not agree, the problem may be in the wiring or wiring connections.
Alternatively, you may highlight particular loops, one at a time, (e.g., loop 4 shown above), then
enter a value of your choice. One approach is to test each loop output using 4, 12, and 20 mA signals
to simulate the 0%, 50% and 100% scale of the specific parameter assigned to that loop. Then follow
the procedure above to test the mA values at the input of the SCADA.
WARNING!
To proceed you need to remove the cover of the 6500 Monitor, which exposes AC power
connections. A qualified electrician should perform the test below.
If the wiring and input connections check okay, focus on the output connector of the 6500 Monitor.
To do this use the “Test 4-20” menu to observe or assign values, then carefully remove the 6500 front
cover using the 4 screws that secure it. Take care not to drop the cover and be sure to leave the blue
ribbon cable connected if you want to refer back to the display. Next unplug the 4-20 mA output
connector (see Figure 2.14 to locate this connector if necessary). Using an ammeter, verify that the 4-
20 mA values agree with the values you read or assign. If these do not agree, the problem may be in
the 6500 circuitry. Contact YSI authorized service for advice. See Section 7, Warranty and Service,
for specific contact information.
YSI Incorporated 6500 Environmental Process Monitor 58