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P&ID pH Controller

P&ID pH Controller P7687

The P7687 offers full P&ID control of the pH in a process.

P7687 pH Controller Introduction

The Model P7687 is a microprocessor based panel mounting pH controller with temperature input for measurement and automatic temperature compensation. Alternatively the P7687 can be user selected to operate as a redox controller for process control applications.

The P7687 can work with a glass pH electrode, industrial pH probe, antimony pH electrode or Glass Redox mV electrode or Industrial Redox Probe.

The P7687 has a multiline graphic display which shows the measured pH and the temperature, as well as the state of the control and alarm relays and is powered from a switch mode power supply from a mains voltage of 86-264 VAC at 50/60Hz.

P7687 Current Outputs

The P7687 is a very sophisticated control instrument designed for integration into process control, water treatment and effluent treatment applications.

For system integrators the P7687 incorporates 2 x isolated 0-20mA or 4-20mA outputs. The 4-20mA outputs can be user configured for either 2 x pH, 2 x mV or 1 x pH and 1 x °C.

The 4-20mA outputs can be user selected to be proportional to a specific range, they can be expanded, or they can be inverted. Making them ideal for use with a PLC, Data logger, or for connecting directly to control equipment including 4-20mA control dosing pumps.

P7687 PID Control and Relay Outputs

In addition to the 0-20mA/4-20mA current outputs the P7687 includes 2 x control relay outputs.

These can be programmed for either On/Off control, PFM control to proportionally control electronic metering pumps, or PWM to time proportionally control solenoid valves.

The control relays feature the option for Proportional Integral and Derivative action (PID) control, with user selectable parameters on both relays.

In addition to the control relays, the controller includes an adjustable alarm relay with delay timer, which can operate on both a high and low measured value. 

As well as the alarm relay, the P7687 includes an auto-clean relay complete with freeze and hold which is designed to work with our pH electrode auto-clean system. The freeze and hold function ensures that the last reading of the instrument is held on screen. The hold function ensures that the control relays and the 4-20mA output are held with the preset value, and then the auto-clean system operates a valve which can control a range of auto-clean systems to prevent coating of the electrode. 

Two logic inputs are available which inhibit the operation of the control and alarm relays so the instrument goes into a standby mode when the logic input is operated. The logic input can be provided by a VFC input from a flow sensor or other sensing device. 

P7687 Features & Benefits

The P7687 is a very modern microprocessor based pH controller, suitable for pH measurement and control applications.

The multiline display is clear and crisp and displays the measured pH value and temperature in the display. The current state of the relay is displayed prominently on the screen, showing the control methodology currently selected and the current value of the distance from the desired set-point in the measured pH.

The control functionality of the P7687 is unparalleled. With either basic on/off control for solenoid valves and pumps, proportional control from PFM, PWM or from a proportional 4-20mA signal, as well as full Proportional, Integral and Derivative (PID) control for pH.

The powerful P7687 is housed in a small panel mounting enclosure measuring 96 x 96 DIN specification and with a case length of just 95mm.

The P7687 is easy to connect and integrate into a system or use as a stand-alone device. The plug-in connectors make both integrating and initial wiring as simple as possible.

Powered from a switch mode power supply from a mains voltage of 86-264 VAC at 50/60Hz, the P7687 is ideal for integration into systems destined for the export market.

The P7687 is a reliable, dependable, and accurate pH controller designed specifically for precision pH adjustment of many process control applications or pH neutralisation processes.

P7687 Specifications

  • Specifications


    Model No:- P7687

    pH Range:- 0-14.00 pH

    Redox Range:- -2000 to +2000 mV (±2000mV)

    Temp. Compensation:- Manual or Auto via 3 wire PT100 / PT1000

    Temp. Range:- -10ºC to 110ºC or 14°F to 230°F selectable

    Input:- pH - Glass pH electrode, Antimony pH electrode, or Redox Electrode and optional Temperature for ATC.

    Set Points & Control Relays:- 2 selectable for:

    • on/off, high / low selectable, 5 amp non-inductive
    • PFM for 0-120 Pulses / Minute
    • PWM with pulse width 0-99.9 seconds
    • PFM or PWM modes with PID control

    Alarm Relay:- 1 x Alarm min / max with 9-99 second delay

    Auto-Clean Relay:-

    • Frequency 0.5 to 100 hours, clean time 1 to 60 seconds
    • Hold time 0.1 to 20 minutes

    Current output:- 2 x 0-20/4-20mA isolated into 600Ω

    Zero:- Adjustable

    Slope:- Adjustable

    Display:- Multi-line Graphic Display 128 x 64 Pixel.

    Mains Supply:- 86 - 264 VAC 50/60Hz.

    Power Consumption:- 6 VA Max.

    Weight:- 450 grams DIN version

    Dimensions:- 98 x 98 x 105mm. Cutout 91.5 x 91.5mm

  • Features


    • Powerful pH controller offering full PID Control of pH in process applications.
    • Dual isolated 4-20mA which can be inverted and expanded as required, with output corresponding to 2 x pH, 1 x pH & 1 x Temp, or 2 x mV. 
    • Sophisticated microprocessor based instrument with a huge array of control options
    • Simple menu driven setup and configuration procedure makes commissioning and calibrating quick and simple.
    • Built in auto-clean relay which can be used to ensure that the pH / Redox / Temperature probe is kept clean in dirty applications.
    • Proportional pH control means that pH can be brought in line using less chemical and precisely controlled for pH critical applications.
    • PID controlled pH ensures accurate and quick pH correction.
    • Works with both pH and Redox, and can also work with Antimony Electrodes, making it perfect for HF (Hydrofluoric Acid) applications.
    • PFM control relay for use with proportional controlled dosing pumps, PWM controlled relay for use with solenoid valves
    • Expandable 4-20mA or 0-20mA output and invertible 4-20mA / 0 - 20mA, meaning that the high and low points can be expressed over a custom range of the pH or Redox scale either for proportional control, or greater resolution over a finite pH scale - particularly useful in critical pH and Redox applications.
    • Alarm relay, delay times, expandable and invertible outputs, all within a precision pH controller - the P7687 is an excellent instrument for even the most complicated pH control tasks.
  • Data Sheets

    Data Sheets


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