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Dual Input pH and Redox Controller

p7685 010 dual input ph controller

The P7685-010 Dual Input pH and Redox Controller is available in both surface mounting and panel mounting configurations.

Dual Input pH and Redox Controller P7685-010 Introduction

The P7685-010 is a dual input pH and Redox (ORP) controller and has inputs for one pH probe, one Redox probe and one Temperature sensor. With these inputs connected to the same controller, space can be saved when requiring separate process instruments. In addition a temperature sensor can be connected to the P7685-010.

The temperature sensor is used to measure temperature and can be used as an automatic temperature compensation (ATC).

The P7685-010 is designed to provide reliable, accurate, dependable and repeatable measurement and control of many industrial processes.

The pH electrode input can be via a standard pH electrode or via an antimony electrode for use in applications where Hydrofluoric acid is present.

The P7685-010 has a range of outputs including 2 x 4-20mA expandable outputs. These 4-20mA current outputs are user configurable and can be selected to give either 2 x pH outputs, or 1 x pH output and 1 x Redox mV output signal, or 1 x pH and 1 x Temperature output.

The display on the P7685-010 dual input pH and Redox controller is a bright 16 character alphanumeric display showing the measured parameter (pH, Redox or Temperature) as well as the state of the control relays and alarm relays.

By simply pushing the front mounted buttons, information is provided regarding the operating condition of the pH sensor, Redox sensor, control, alarm and output parameter settings.

For pH measurement the P7685-010 dual input pH and Redox controller offers a full range across the 0.00-14.00 pH scale, from 0 - ±1000mV on the Redox or ORP scale and - 10 to 110ºC on the temperature scale.

We strongly recommend pairing the P7685-010 with an AWE Instrument, either pH Electrode or Redox Electrode as required, or another high quality electrode.

The versatility of the microprocessor and the user friendly software allow the programming of the dual input pH and Redox controller to be as easy as possible. The calibration of the instrument is simple, allowing this to be conducted even by untrained operators.

P7685-010 Dual input pH and Redox Controller with Proportional Control Relays

The P7685-010 dual input pH controller is fitted with two proportional control relays which can be programmed for either On/Off Control, PFM control for use with a proportionally controlled dosing pump, or PWM to proportionally time control solenoid valves.

The two setpoint relays can be used for either pH or Redox. That is, both relays can be set for pH control, or one for pH control and one for Redox Control or both for Redox Control.

The proportional control relays are band selectable across the output range. This means that a compatible dosing pump, such as our range of proportional control AT-AM series dosing pumps,  can be called to adjust the number of strokes or frequency of strokes that the pump makes per minute. This allows the pump to precisely control the amount of chemical dosed as well as decreasing the amount of chemical used and enabling the pH Controller and a correctly matched dosing pump to reach a precise pH value.

In addition, the control relays for the P7685-010 dual input pH and redox controller has a single alarm relay with delay timer. This can be set to either a high or low measured value on the pH input or Redox (ORP) input.

There is also an auto-clean relay fitted to the controller. This auto-clean relay can be used to control one of our auto-clean systems. These are systems which use a blast of compressed air to remove debris or coatings which may cover a process electrode which in this instance could be either a pH probe or Redox probe.

The P7685-010 dual input controller will freeze and hold the measured values as well as the control function for a pre-set time during this process. This is designed to ensure that the output controls and output signals do not cause a false reading to initiate a new process or simply give a false reading.

P7685-010 Dual input pH and Redox Controller with dual expandable 4-20mA Outputs

The P7685-010 Dual input pH controller has two expandable 4-20mA outputs.

These 4-20mA outputs are expandable (programmable) into 600Ω and can be used to feed directly into a programmable logic controller (PLC) or to compatible control devices such as our 4-20mA Dosing Pumps.

The 4-20mA outputs can be selected so that the output signal corresponds to either 2 x pH, or 1 x Redox and 1 x pH, or 1 x pH and 1 x Temperature. In addition one of the 4-20mA outputs can be disabled should it not be required.

As the 4-20mA outputs are expandable they can be programmed to represent a smaller amount of the required scale or be  inverted. That is with pH. As an example, a 20mA current output signal could be given at a value of 10.00 pH and a value of 7.00 pH could represent 4mA. This would call for a compatible dosing pump to dose a correcting acid to bring the pH down to 7.00 should the pH exceed this value.

Normally a compatible pump would be programmed to offer the maximum number of strokes per second at the 20mA value and to stop should a 4.00mA signal be received. The P7685-010 Dual input pH and Redox controller can also offer a user defined hysteresis of ±10%.

P7685-010 Specifications

  • Specifications


    Model No:- P7685-010

    pH Range:- 0-14.00 pH

    Redox Range:- -1999 to +1999 mV

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

    Temp. Range:- -10ºC to 110ºC

    Input:- One for pH, either Glass pH electrode, or Antimony pH electrode, second input for Redox Electrode and a third for Temperature display - PT100

    Set Points:- 2 on/off, high/low selectable, 5 amp inductive

    Action:- On/Off, PFM, PWM, and with delay timer

    Other Relays:- Alarm, Auto-Clean Relay

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

    Zero:- Adjustable

    Slope:- Adjustable

    Mains Supply:- 230 Volt / 115 Volt, 50/60Hz.

    Power Consumption:- 5 VA

    Weight:- 850 grams DIN version

    Dimensions:- 96 x 96 x 155mm cutout 91.5 x 91.5mm

  • Features


    • Measures and control both pH and Redox in the same instrument
    • A 4-20mA output for use with pH, and a separate 4-20mA output for use with either temperature or Redox
    • Sophisticated microprocessor based instrument with a huge array of control options
    • Despite the array of options the P7685 has a simple menu driven setup and configuration procedure
    • 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.
    • 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 P7685 is an excellent instrument for even the most complicated pH control tasks.


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