The model P7335 is our small case pH controller and is a member of our series 7335 analytical instruments. The 7335 series are housed in 48 x 96 din standard enclosures which are only 95mm deep, designed for mounting in panels where space is at a premium.

The P7335 pH/Redox (ORP) millivolt controller features selectable ranges for pH with a glass electrode, as well as pH using an Antimony electrode which maybe used in solutions containing HF acid and also Redox (ORP) millivolts over the range of - 1000 mV to +1000 mV.

Temperature compensation maybe manually set over the range of 0–100ºC or automatically compensated for over the range of 0-100ºC by the use of either a Pt100 or Pt1000 temperature sensor which is user selectable. A bright red LED indicates the selected parameter pH or mV, the main readout features a 4 digit red LED display, which provides excellent visibility and provides the user with messages for setup and operation.

The front panel includes 4 keys that allow the user to access the most frequently used functions. Two programmable control relays are fitted, the control relays can be programmed for either high or low operation and have adjustable delay timers. One adjustable alarm relay with delay timer is fitted which maybe set to operate on both a high and low measured value.

The isolated current output corresponds to the measuring range selected and can be selected for either 0-20mA or 4-20mA. The versatility of the microprocessor accompanied by the user friendly software allows the programming of the functions, routine checks and calibration to be easily accomplished even by untrained operators. Installation of the 7335 series of instruments is intended to be in a control panel or in the optional surface mounting enclosure.

The rear of the case is fitted with removable connector blocks for ease of installation and maintenance.

4-20mA output for use with PLC's and Chart Recorders

The P7335 small size pH Controller has an isolated current output which corresponds to the measuring range selected (either pH Control or Redox Control) and can output either a 0-20mA or a 4-20mA signal. The current output is non-expandable and is most commonly used with a PLC or Chart Recorder.

The P7685 pH controller for proportional dosing is available in either panel mounting or surface mounting configuration.

P7685 pH Controller For Proportional Dosing Introduction

The P7685 pH controller is designed to provide reliable, accurate, repeatable and dependable measurement and control of industrial pH processes.

For those applications where precise control is required our model P7685 pH controller is the ideal partner featuring two proportional outputs, an expandable 4-20mA output and an alarm relay with delay timer.

The 16 character alphanumeric LCD displays the measured parameter and provides information about the state of the control and alarm relays.

Also accessible is an indication of the operating condition of the sensor. The versatility of the microprocessor accompanied by the user-friendly software allows the programming of the functions, routine checks and calibration to be easily accomplished even by untrained operators.

The model P7685 pH controller is a microprocessor panel mounting pH/mV & Temperature instrument. The controller is designed for control panel mounting in a 92 x 92mm din standard cutout and is also available as a surface mounting instrument.

The unit operates from a power supply of either 110 VAC or 230 VAC 50/60Hz. The model P7685 pH controller is able to measure and proportionally control pH or Redox (ORP) millivolt.

The measuring discipline is user selectable and the pH input is also selectable for either Glass pH Probes or Antimony pH Probes.

The temperature input provides both a selectable temperature indication and auto temperature compensation of the pH range. The P7685 controller is able to measure pH across the 0.00 - 14.00 pH scale, ±1000mV on the Redox (ORP) millivolt scale and from -10ºC - +110ºC on the temperature scale.

The temperature measurement and Automatic Temperature Compensation are available through the use of a Pt100 temperature sensor. These are available from AWE Direct as either a pH Electrode with a built in Temperature Sensor, or as a separate stand alone temperature sensor.

When measuring pH we suggest pairing our instrumentation with an AWE pH electrode or another good quality electrode. For Redox measurement we recommend pairing the P7685 with an AWE Platinum band Redox Probe or another precision Redox probe. We also have Antimony pH Probes for use with applications where Hydrofluoric Acid may be present.

Proportional Control Relays, PFM, PWM, or On/Off Control and Alarm Relay.

The model P7685 pH controller features two control relays which can be programmed for either On/Off control, PFM control to proportionally control electronic metering pumps or PWM to time proportionally control solenoid valves or small pumps.

The P7685 is also fitted with an adjustable alarm relay with delay timer. This can operate on both a high and low measured value.

The P7685 proportional control relays offer PFM (pulse frequency modulation) output for proportional control of our electronic dosing pumps. The P7685 has adjustable set points and proportional band selectable for either one acid and one alkali-dosing pump.

In this instance the pH value of the measured solution can be efficiently corrected using either an acid dosing pump and an alkali dosing pump. For a pH value below the desired setpoint (e.g. a measured value of 6.00pH requiring correcting to a value of 7.00pH) the P7685 controller would call for the alkali metering pump to dose. When correcting from a value of 8.00pH to 7.00pH the P7685 controller would call for the acid dosing pump to dose.

The PFM output signal from the P7685 will mean that the a compatible dosing pump such as our ATAM series will automatically vary the frequency or number of strokes the pump makes per minute. As the pH scale is logarithmic, the amount of chemical required to correct from a pH of 5.00 to 7.00 is ten times greater than the amount of chemical required to correct from 6.00 to 7.00 pH.

Using a proportional control pH controller like the P7685 means that when correcting from 5.00pH to 7.00pH the controller will call for the pump to dose at a much higher rate when initially correcting from 5.00 pH and as the measured value reaches 7.00 pH the controller will call for the pump to dose a small amount or less frequently to ensure that the required pH value is both reached precisely and the amount of correcting chemical being dosed is delivered as efficiently as possible.

The P7685 pH controller for proportional dosing is also able to be setup for a duty and assist type installation. This is particularly useful in a number of applications specifically when a certain pH value has to be reached quickly or held during process control.

For instance if a pH value of 2.00 pH has to be maintained during a process - the P7685 can operate two different pumps both dosing a strong acid. Normally one of these would be a dosing pump with a large output and the second being a small dosing pump.

The larger of the pumps can be proportionally controlled to bring the pH down to a level close to 2.00 pH (approximately 2.50 pH), then a second pump could be called to trim the pH to the desired level of 2.00 pH. Depending on the process and whether the pH value rises during the process, either the smaller or the larger pump can be called to efficiently maintain the required pH value; (2.00 pH in this example.)

pH controller with expandable 4-20mA for proportional control

The P7685 pH Controller 4-20mA proportional output is an industry standard current output signal which can be used with a number of compatible devices including PLC's, Data-loggers, and other associated items.

The P7685 pH Controller with an expandable 4-20mA output signal, means that the 4-20mA output can either represent the full 0-14.00 pH scale or a proportion of the range. So for instance the 4-20mA can be set over the 7.00 to 10.00 pH range where a 4mA is produced at 7.00 pH and a 20mA signal is produced at the 10.00 pH value.

By incorporating an expandable 4-20mA signal the pH controller can work with an input device such as a dosing pump or another piece of control equipment. This could be used to proportionally control the pH value by either increasing the frequency or number of strokes the pump makes per minute to allow for precise control and efficient use of chemical.

The isolated output corresponds to the measuring range selected which will expand in units of 1pH and can be programmed for either 0-20 mA or 4-20 mA. The P7685 pH controller for proportional dosing in either panel mounting or surface mounting configuration with two control points on/off, PFM for proportional control of dosing pumps or PWM for proportional control solenoid valves, alarm relay with delay timer and isolated and expandable 0 (4) -20 mA current output has the electronics housed into an anodised aluminium case providing excellent EMC properties, and the rear of the case is fitted with two plug-in connector blocks for ease of installation and maintenance.

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%.