Crimson: PID Module Basics

06 Jun 2025

Industrial Automation Tech Note 09 - TNIA09

Abstract

This document describes the basic parameters and common functionality of the Crimson based PID controllers.

Products

CSPID1xx, CSPID2xx, CSSGxxxx, GMP1xxxx, GMP2xxxx

Use Case

Configuring systems that incorporate Crimson based PID controllers.

 

Commonly Used Parameters

Loop – Status – PV

Loop – Control – ReqSP

Loop – Status – HeatPower/CoolPower

Loop – Control – Power

Loop – Control – ReqManual

Loop – Control – ReqTune

Loop – Status – TuneDone

Loop – Status – TuneFail

Loop – Status – ActSP

Loop – Status – AckManual

Loop – Status - AckTune

Turning the Loop Off

Properly turning off a loop will prevent loss of control when set point control is once again required.

Required Module Properties

Loop – Control – ReqManual

Loop – Control – Power

Optional Module Properties

Loop – Status – AckManual

Action

1. Set ReqManual to 1

2. Set Power to 0

Example: ReqManual = 1, Power = 0

Manual Control of the Loop

Properly turning off a loop will prevent loss of control when set point control is once again required.

Required Module Properties

Loop – Control – ReqManual

Loop – Control – Power

Optional Module Properties

Loop – Status – AckManual

Action

1. Set ReqManual to 1

2. Set Power to the required output level 0-10000 (0-100.00%)

Autotuning the Loop

Required Module Properties

Loop – Control – ReqTune

Loop – Control – ReqSP

Loop – Status – TuneDone

Optional Module Properties

Loop – Status – AckTune

Loop – Status – PV

Action

1. Set ReqTune to 1

2. Monitor TuneDone, when it becomes true, set ReqTune to 0.

Fig_1.png

Figure 1.

Note: Referring to Figure 1, adding an Active On Trigger to the tag mapped to TuneDone with an action to clear ReqTune is recommended.

Overview

Auto-tune may be used to establish the optimal P, I, D, and Power Filter values. By cycling the process through four on/off cycles, the module learns information about the process and determines the best values.

Fig_2.png

Figure 2.

As shown in Figure 2, the setpoint used during auto-tune is the value 75 % above the difference between the current PV and the setpoint. This allows the oscillations to occur close to setpoint, while avoiding excessive overshoot. Since the module performs on/off control during auto-tune, it is important to set a suitable On/Off Hysteresis value prior to invoking auto-tune.

Customization of the PID set that auto-tune will yield is achieved by adjusting the Tune Response setting. The Tune Response setting can be set to Very Aggressive, Aggressive, Default, Conservative, or Very Conservative. Further, the Tune Response setting can be adjusted by writing 0-4 respectively to the Tune Response register.

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.

Red Lion Technical Support

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