Emerson 54e pH/ORP instruction manual PID Control Code, Measurement and Set Point Feedback Control

Page 56

MODEL 54e pH/ORP

6.9PID CONTROL (CODE -20)

PID Control

The Model 54e pH/ORP current outputs can be pro- grammed for PID control. PID control is used with a control device which is capable of varying its output from 0 to 100 percent in response to a changing sig- nal in milliamps. Automated control valves or vari- able volume pumps are commonly used. These types of devices are referred to as modulating con- trol devices because of their 0 to 100% adjustability. PID control is typically used where greater accuracy than is achievable with an on/off device is required, or where it is desirable to have the pump or valve "on" continuously, or where the existing or preferred pump or valve is of the modulating type.

Any process control system must manually or auto- matically hold the controlled variable (pH, conductiv- ity, temperature) in a steady condition at selected set point values. For manual control, the operator looks at the value of the process variable, decides whether or not it is correct, and makes necessary adjustments. He decides the amount, direction, rate of change and duration of the adjustment. With auto- matic control, the controller does all of this. The operator only adjusts the set point of the controller to the selected value of the measured variable. Automatic process control such as PID is usually feedback control; it eliminates the deviation between measurement and set point based on continuous updates (feedback) from the process itself.

SECTION 6.0

THEORY OF OPERATION

Measurement and Set Point (Feedback Control)

The Model 54e pH/ORP controller is given two items of information: measurement and set point. The con- troller reacts to the difference in value of these two signals and produces an analog output signal to eliminate that difference. As long as the difference exists, the controller will try to eliminate it with the output signal. When measurement and set point are equal, the condition of the controller is static and its output is unchanged. Any deviation of measurement from set point will cause the controller to react by changing its output signal.

PID Control Mode Combinations

All PID controllers have several control modes which can be used in various combinations: proportional plus integral (reset), proportional plus derivative (rate) and a combination of proportional (P), integral

(I)and derivative (D). Each control mode produces a response to the deviation of measurement from set point that is the result of a specific characteristic of the deviation, and each control mode is separately adjustable. D, the derivative, or rate mode, is seldom used in water treatment and is beyond the scope of this manual.

50

Page 55 Page 57
Image 56
Page 55 Page 57
Contents PH/ORP Hart Analyzer/Controller Model 54e pH/ORPEssential Instructions Electrical Shock HazardPage Section Title Description and SpecificationsModel 54E PH/ORP Microprocessor Analyzer Table No Title Appendix TitleList of Tables Table of Contents List of Figures About This DocumentDescription of Controls Section Description and SpecificationsGeneral Description Specifications Physical Specifications General PowerRelative Humidity 95%, non condensing Alarms Current OutputsAnalyzer Specifications @ 25C Recommended SensorsPart NO. Description Ordering InformationCode Options Section Installation Mechanical InstallationLocating the Controller Unpacking and InspectionPanel Mounting Section Wiring Power Input WiringAnalog Output Wiring Alarm Relay Output Wiring454EPH02 Tions will Result in Controller MALFUNC- Tion PH Sensor WiringPH Sensor Compatibility 454EPH01 Cable Dressing Final Electrical Check Wiring to Model Section Calibration IntroductionTemperature Calibration Hold Mode OffAdjust temp 25.1 C Automatic TWO-POINT Calibration Autocal bufferBuffer 1 -- Wait Calibration Notes Auto buffer cal doneUse the arrow keys to select the correct buffer Calibrate point Pt 04.00pH 25CPt calibration done Manual TWO-POINT CalibrationStandardize 7.01 pH SINGLE-POINT pH CalibrationTemperature Compensation Options Temp comp AutoOutput trim 59.16 mV/pHTrim Outputs Hold ModeOutput trim Section Software Configuration PH Settings ListRanges Factory Settings User Settings Diagnostics Section Outline of Menu Levels Alarm High 14.00pH Changing Alarm SetpointsSimulate tests Setpoint 07.00 pHSetpoint 7.00 pH 4mA 0.00 pH 20mA 2.00 pHSetpoint + 06.90 pH Changing Output Setpoints PID onlyOutput OutputMA 0.00 pH 20 mA 14.00 pH Output 1 12.00 mA MA +00.00 pHAlarm setpoints Output setpoints Test output Test alarmTesting Outputs and Alarms Simulated testsTest alarm 1 Open Test alarm 1 OpenDisplay right AL2 Measure pHDisplay contrast Timeout On Security CautionControl Mode DisplayChanging Output Parameters Output Control ParametersRange 4-20 mA Fault 22.00 mARange 4-20 mAl Fault 22.00mA Output 2 control Output 2 setupHold feature setup Hold Disable featureInterval timer AlarmsAlarm 3 control Alarm Low Setpoint 0.01 pH Delay 0 secHysteresis 0.01 pH Delay 0 sec Relay Default NoneRelay default None Setpoint +07.00 pHTime period 30 sec URV 2.00 pHAlarm Fault Feed limit DisableTimeout 3600 sec Alarm 4 SetupOn time 120 sec Timer DisableRecovery 600 sec Interval Timer Examples Zero offset 60 mV DiagnosticsDiagnostics Off Diagnostics Auto Calibration SetupAutocal Standard Stabilize pH 0.01 pH Stabilize time 10 secAuto Calibration Setup Standard BuffersContinuous Sensor Diagnostics Section Theory of OperationSee .8 for instructions on chang- ing these setpoints Interval TimerTypical set points Alarm Relays Time Proportional Control TPC Mode CodeNormal Mode Analog OutputsController Mode Priority Controller Mode Priority ChartCondition Definitions Action DefinitionsPID Control Mode Combinations PID Control CodePID Control Measurement and Set Point Feedback ControlControl Loop Adjustment and Tuning Proportional Mode GainProportional Gain Plus Integral Reset Process Reaction Curve Method Process Reaction CurvePID Control Level 1 3 Password Privileges Section Special Procedures and FeaturesPassword Protection Configuring Security SecurityCustom Curve Lock allSensor iso 07.00 pH Solution Temperature CompensationTemp coeff +.000 Operate iso +07.00 pH Section Troubleshooting Troubleshooting is easy as 1, 2, 3…Diagnostic Messages Diagnostic Messages Description of problemQuick Troubleshooting Guide Symptom ActionDiagnostic Variables Theoretical pH vs. Millivolt Values at 25C 77F Troubleshooting Guidelines Temperature Compensation CircuitTroubleshooting Procedure Ohms Ambient TemperatureController preamp check Figure Preamplifier Troubleshooting ProcedurePreamp in a junction box Figure Junction Box Preamplifier Check Troubleshooting Guide No PowerCoated glass electrode Clean with soft cloth and clean water Password protected Replacement Parts Part Number DescriptionWarranty Repair NON-WARRANTY RepairSection Return of Material GeneralAppendix a ORP Configuration Quick Startup ORPTable A-1. ORP Settings List Item Choices ORP Settings User SettingsChoices ORP Settings User Settings Diagnostics SectionOutput setpoints Simulated testsStandardize 400 mV ORP CalibrationReturn of Materials Request Sensor or Circuit Board onlyWarranty Return of MaterialSpecifications subject to change without notice
Top Page Image Contents