Emerson 54e pH/ORP instruction manual Alarm Relays, Time Proportional Control TPC Mode Code

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MODEL 54e pH/ORP

SECTION 6.0

 

THEORY OF OPERATION

6.4 ALARM RELAYS

An alarm is a relay that closes a set of contact points (a switch) inside the controller. In doing so, the relay clos- es an electrical circuit and turns on a device wired to the contacts. The Model 54e pH/ORP controller has four alarm relays.

The relays are turned on and off by the controller based on the control points or setpoints that you pro-gram into the controller through the keypad. See Section 5.7 "Alarms" to program the alarm relays.

The Model 54e pH/ORP has two control modes for de- vices which are turned off and on: Time Proportional Control Mode (TPC), and Normal Mode. TPC is gener- ally used for chemical feed control. Normal or "on-off" mode is typically used to control external alarm lights or horns.

6.5TIME PROPORTIONAL CONTROL (TPC) MODE (Code -20)

In the TPC mode, you must establish the following parameters which will determine how the Model 54e pH/ORP responds to your system (see Section 5.7):

•Setpoint

•Time period

•URV point (or 100% on)

•LRV point (or 0% on)

•Proportional

•Integral

•Derivative

The setpoint is the desired value that you want to con- trol at. Time period is programmed in seconds and de- fines the interval during which the controller compares the pH input from the sensor with the Setpoint. In the TPC mode the controller divides the period up into pump on-time (feed time) and pump off-time (blend time).

The URV setting determines how far the pH must devi- ate from the setpoint to get the pump to be on for the entire period. The LRV setting determines how close the pH must be to the setpoint for the pump to be off for the entire period. The LRV setting should always be set at zero. When the error (the pH minus the setpoint) is between the URV and LRV values, the relay will be en- ergized for some portion of the time period. As the pH

FIGURE 6-1. Time Proportional Control

value approaches the setpoint, the pump will be feed- ing for shorter and shorter intervals, and the chemicals will be allowed to mix for longer and longer intervals of the period. This relationship is illustrated in Figure 6-1.

The exact amount of on time and off time per period is determined by the settings for proportional, integral, and derivative bands. The proportional band (P) in % is a separate adjustment that narrows (or widens) the range of the TPC 0-100% action. Smaller values are used for more control response. For a setpoint of 7 pH, a URV of 2 pH, and P=100%, a pH reading of 8 would result in a relay on (8-7)/((2-0)*(100%)) or 50% of the time. If P was changed to 50%, the same relay would be on (8-7)/((2-0)*50%) or 100% of the time.

The integral band is set in seconds and acts to increase the controller output as more time is spent away from the setpoint. A smaller value in seconds will result in faster integration response. Too low a value will result in excess oscillation.

The derivative band is set in % and acts to prevent changes in the reading. This setting should generally be set to zero for pH and ORP applications.

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Contents Model 54e pH/ORP PH/ORP Hart Analyzer/ControllerElectrical Shock Hazard Essential InstructionsPage Section Title Description and SpecificationsModel 54E PH/ORP Microprocessor Analyzer Table No Title Appendix TitleList of Tables About This Document Table of Contents List of FiguresDescription of Controls Section Description and SpecificationsGeneral Description Power Specifications Physical Specifications GeneralRelative Humidity 95%, non condensing Alarms Current OutputsRecommended Sensors Analyzer Specifications @ 25CPart NO. Description Ordering InformationCode Options Mechanical Installation Section InstallationLocating the Controller Unpacking and InspectionPanel Mounting Power Input Wiring Section 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 Introduction Section CalibrationTemperature 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 Pt 04.00pH 25C Calibrate pointPt calibration done Manual TWO-POINT CalibrationSINGLE-POINT pH Calibration Standardize 7.01 pHTemp comp Auto Temperature Compensation OptionsOutput trim 59.16 mV/pHTrim Outputs Hold ModeOutput trim PH Settings List Section Software ConfigurationRanges Factory Settings User Settings Diagnostics Section Outline of Menu Levels Changing Alarm Setpoints Alarm High 14.00pHSimulate tests Setpoint 07.00 pH4mA 0.00 pH 20mA 2.00 pH Setpoint 7.00 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 pHTest output Test alarm Alarm setpoints Output setpointsTesting Outputs and Alarms Simulated testsTest alarm 1 Open Test alarm 1 OpenMeasure pH Display right AL2Security Caution Display contrast Timeout OnDisplay Control ModeChanging Output Parameters Output Control ParametersRange 4-20 mA Fault 22.00 mARange 4-20 mAl Output 2 control Output 2 setup Fault 22.00mAHold feature setup Hold Disable featureInterval timer AlarmsAlarm 3 control Setpoint 0.01 pH Delay 0 sec Alarm LowHysteresis 0.01 pH Delay 0 sec Relay Default NoneSetpoint +07.00 pH Relay default NoneTime period 30 sec URV 2.00 pHFeed limit Disable Alarm FaultTimeout 3600 sec Alarm 4 SetupOn time 120 sec Timer DisableRecovery 600 sec Interval Timer Examples Zero offset 60 mV DiagnosticsDiagnostics Off Auto Calibration Setup DiagnosticsAutocal Standard Stabilize pH 0.01 pH Stabilize time 10 secStandard Buffers Auto Calibration SetupSection Theory of Operation Continuous Sensor DiagnosticsSee .8 for instructions on chang- ing these setpoints Interval TimerTypical set points Time Proportional Control TPC Mode Code Alarm RelaysAnalog Outputs Normal ModeController Mode Priority Chart Controller Mode PriorityCondition Definitions Action DefinitionsPID Control Code PID Control Mode CombinationsPID Control Measurement and Set Point Feedback ControlControl Loop Adjustment and Tuning Proportional Mode GainProportional Gain Plus Integral Reset Process Reaction Curve Process Reaction Curve MethodPID Control Level 1 3 Password Privileges Section Special Procedures and FeaturesPassword Protection Security Configuring SecurityCustom Curve Lock allSensor iso 07.00 pH Solution Temperature CompensationTemp coeff +.000 Operate iso +07.00 pH Troubleshooting is easy as 1, 2, 3… Section TroubleshootingDiagnostic Messages Description of problem Diagnostic MessagesSymptom Action Quick Troubleshooting GuideDiagnostic Variables Theoretical pH vs. Millivolt Values at 25C 77F Temperature Compensation Circuit Troubleshooting GuidelinesTroubleshooting Procedure Ohms Ambient TemperatureController preamp check Figure Preamplifier Troubleshooting ProcedurePreamp in a junction box Figure Junction Box Preamplifier Check No Power Troubleshooting GuideCoated glass electrode Clean with soft cloth and clean water Password protected Part Number Description Replacement PartsNON-WARRANTY Repair Warranty RepairSection Return of Material GeneralQuick Startup ORP Appendix a ORP ConfigurationItem Choices ORP Settings User Settings Table A-1. ORP Settings ListDiagnostics Section Choices ORP Settings User SettingsSimulated tests Output setpointsORP Calibration Standardize 400 mVSensor or Circuit Board only Return of Materials RequestReturn of Material WarrantySpecifications subject to change without notice
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