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CNT-SVX08F-EN
49
Troubleshooting
The analog output generates a 0–10 Vdc control signal used to control valve, damper, pump speed,
fan speed, and so on. The PID loop in the MP501 calculates a value between 0 and 100%. The
controller then translates that percentage into the output voltage.
lists the scaling for
typical analog output applications. This information will help to anticipate the voltage that is read,
given the PID output.
Table 20. Percent to voltage scaling for analog output
PID Output
Voltage Output
(0–10 Vdc Output)
Voltage Output
(2–10 Vdc Output)
0%
0.0 Vdc
2.0 Vdc
25%
2.5 Vdc
4.0 Vdc
50%
5.0 Vdc
6.0 Vdc
75%
7.5 Vdc
8.0 Vdc
100%
10.0 Vdc
10.0 Vdc
The troubleshooting steps in
assume the end device connected to the analog output is
always closed when the user believe it should be somewhat open and vice versa when closed.
Table 21. Analog output (0–10 Vdc) troubleshooting of external wiring
Step Number
Action
Probable Cause
Step 1
Perform the initial troubleshooting steps described in
and verify general board
operation is okay.
General board
problem.
Step 2
Inspect the wiring. Is there a good connection between the wire and the terminal blocks? Look
for shorts or opens. Pay particular attention to wire splices.
Wiring problem.
Step 3
Take your meter (set to measure dc voltage) and measure the voltage across the AO terminals
on the MP501.
If you see a value greater than 0 V, the problem lies beyond the MP501. Is the wiring to the
equipment good? Is there a hardware override controlling the equipment?
If you see approximately 0 V, proceed to the next step.
Wiring problem.
Step 4
Remove the wires from the AO terminals and measure the voltage again.
If you see a value greater than 0 V, there is a wiring or equipment problem external to the
MP501.
If you still see approximately 0 V, the MP501 is commanding the output to be closed and you
need to investigate the MP501 further.
Wiring problem.
If the analog output is still not opening the end device, then follow the additional troubleshooting
steps in
. These steps will assist the configuration and operation of the analog
output.