# Process Control Tech Note 01 - TNPC01

## Abstract:

This document explains two different procedures for manually tuning PID controllers.

## Products:

All PID Controllers

## Use Case: Manually Tuning PID Controllers

There are a variety of ways to tune PID loops, this document describes two different manuak tuning procedures.

## PROCEDURE 1:

### Simple Manual Tune Procedure with Very Little or No System Oscillation During the Tune Procedure

• Lower the derivative value to 0, we will not change this value from zero after this first step.

• Lower the integral value to 0, easy second step.

• Raise the proportional value 100.0

• Increase the integral value to 100

• Slowly lower the integral value and observe the system’s response.

• Since the system will be maintained around setpoint, change setpoint and verify if system corrects in an acceptable amount of time. If not acceptable or you would like a quick response, continue lowering the integral value.

• If the system begins to oscillate again, record the integral value and raise value to 100. Just like me, you got a little greedy trying to get the quickest response.

• After raising the integral value to 100, return to the proportional value and raise this value until oscillation ceases.

• Lower the proportional value back to 100.0 and then lower the integral value slowly to a value that is 10% to 20% higher than the recorded value when oscillation started. (recorded value times 1.1 or 1.2)

Change the setpoint and watch as the system tracks quickly and efficiently. If you experience an overshoot that is not desirable, consider using the setpoint ramp parameter. It is most useful at system start-up or when a large setpoint change is introduced during system operation.

## PROCEDURE 2:

### Utilizing the System Oscillation to Determine Optimum Proportional and Integral Values.

During this procedure, you are going to locate the ultimate gain value utilizing the proportional value only. Then you will introduce error correction with the integral value. As you can see above, the rate of change, or derivative value, may be more of a nuisance. You will have to move back and forth between the parameters, mostly proportional and integral, with an occasional setpoint change as we manually tune the unit.

This may seem as a tedious process to complete a manual tune of a quick responding system, but surprisingly you will complete the process in a reasonably short time period with acceptably tight control results.

• Lower the derivative value to 0, we will not change this value from zero after this first step.

• Lower the integral value to 0, easy second step.

• Raise the proportional value to a high value, I often use 150.0

• Change the setpoint value to develop a difference between actual process value and setpoint value.

• Lower the proportional value slowly. You may see some correction but there will always be a difference between the process value and the setpoint value you programmed (steady state error).

• As you lower the proportional band slowly, you increase the risk of initiating a system oscillation. If oscillation becomes large and is not acceptable, record the proportional band value and then raise the band value until oscillation ceases.

• Since the proportional band has been raised to stop the system oscillation, this is a good time to raise the integral value to 100. Eventually we will use the integral value for error correction.

• Return to the proportional band and lower the value slowly until a value that is double of the earlier recorded value is reached.

• Now lower the integral value slowly and the error between setpoint value and process value will decrease.

• Since the system will be maintained around setpoint, change setpoint and verify if system corrects in an acceptable amount of time. If not acceptable or you would like a quick response, continue lowering the integral value.

• If the system begins to oscillate again, record the integral value and raise value to 100. Just like me, you got a little greedy trying to get the quickest response.

• After raising the integral value to 100, return to the proportional value and raise this value until oscillation ceases.

• Lower the proportional value to the double value used earlier in the set-up and then lower the integral value slowly to a value that is 10% to 20% higher than the recorded value when oscillation started. (recorded value times 1.1 or 1.2)

Change the setpoint and watch as the system tracks quickly and efficiently. If you experience an overshoot that is not desirable, consider using the setpoint ramp parameter. It is most useful at system start-up or when a large setpoint change is introduced during system operation.

#### Disclaimer

It is the customer's responsibility to review the advice provided herein and its applicability to the system. Red Lion makes no representation about specific knowledge of the customer's system or the specific performance of the system. Red Lion is not responsible for any damage to equipment or connected systems. The use of this document is at your own risk. Red Lion standard product warranty applies.

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