<Toc> < 4. Troubleshooting and Maintenance >
4-5
IM 05D01C02-41E 3rd Edition: May 31, 2006-00
■ Troubleshooting When the Controller Fails to Operate Correctly
If your control tasks are not successful, check the preset parameters and controller wiring
before concluding the controller to be defective. The following show some examples of
troubleshooting you should refer to in order to avoid the possibility of other problems.
● The controller does not show the correct process variable (PV).
• The UT550/UT520 controllers have a universal input.
The type of PV input can be set/changed using the parameter “IN1”. At this point, the
controller must be wired correctly according to the selected type of PV input. Check
the wiring first if the controller fails to show the correct PV value. To do this, refer
to “2. Initial Settings”.
With the parameters “RH1”, “RL1”, “DP1”, “SH1” and “SL1”, it is possible to scale the
input signal and change its number of decimal places. Also check that these param-
eters are configured correctly.
● The controller does not provide any control output or the control output
does not change at all.
• The UT550/UT520 controllers have a universal output.
The type of control output can be set/changed using the parameter “OT1”.
At this point, the controller must be wired correctly according to the selected type of
control output. Check the wiring first if the controller provides no control output. To do
this, refer to “1.5 Terminal Wiring Diagrams”.
With the parameters “OH” and “OL”, it is possible to set/change the high and low limits
of control output. The control output may not change at all, however, because of
restrictions on these parameters. Also check the restrictions on these parameters.
• The control output can only be changed when the controller is in the MAN mode.
If the MAN lamp is off (i.e., the controller is in the AUTO mode), you cannot change the
control output using key operation.
● The control output does not change soon after the target setpoint SP has
been changed.
• If this happens, check the setpoint of the parameter “MOD”. In cases where fixed-
point control is selected as the PID control mode (MOD = 1), tracking based on the I-
term works to prevent the control output from changing suddenly even if the target
setpoint SP is varied.
The control output therefore may appear to be working incorrectly at first; however it
gradually adapts itself to the new target setpoint.
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