Sterlco M2B+ Controller - Manual (Page 25)

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Manual Tuning (Zeigler-Nichols PID Method)
This tuning method may be used if the spread between ambient temperature and process
operating temperature is small. For best results, use a recording device when tuning with this
method.
1. Disable the cooling valve by removing the output signal to the device. For solenoid
valves, remove plug from the solenoid. For modulating valves, remove the J7 plug
located on the back of the controller.
2. Press the Index button one time to access the Primary Menu.
3. Press the Enter button.
4. In the Primary Menu, change the Reset Time and Rate Time OFF, and change the
Prop Band Heat to 100.
5. Adjust setpoint to the desired value.
6. While monitoring the process temperature or recording device, decease the
proportional value by repeatedly halving the value until a small, sustained
temperature oscillation is observed. Measure the period of one cycle of oscillation
“T”.
7. Divide the period of oscillation “T” by eight; the resulting number is the correct Rate
Time in seconds.
8. Multiply the Rate Time by four. This is the correct Reset Time in seconds.
9. Multiple the bandwidth value “T” by 1.66, and enter this as the new Prop Band Heat
value.
10. Re-enable the cooling valve by reversing step 1.
4-5 Selecting a Local Probe
The controller has two standard temperature probe inputs for delivery (to process) and return
(from process). The probes are typically set up at the factory, but they can be re-configured in
the field. To set up this feature you must have access to the Secure Menu. See Section 2-6 on
page 16 to review accessing the Secure Menu.
Use the following procedure to select a local probe:
1. Press the Index button three times to access the Secure menu.
2. Press the Enter button.
3. Press the Index button until the display reads “Sensor type = RTDIK.”
4. Use the Up and Down buttons to select the sensor type.
5. Press the Enter button to accept the value.
When changing the sensors from RTDs to thermocouples, you must also change the
jumpers JMP1 and JMP3 to pins 2 and 3.
6. Press the Alarm Silence button to return to Running mode.