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Turbidity Controller with Auto-Clean

turbidity controller with auto clean

The TU7685 Turbidity Controller with auto-clean relay is available in either panel mounting or surface mounting configuration.

TU7685 Auto-Clean Turbidity Controller Introduction

The TU7685 Turbidity controller is designed to provide accurate turbidity measurement from a compatible Turbidity Sensor.  In addition to providing a digital indication of the Turbidity measurement on the LCD (Liquid Crystal Display) it also provides a number of set-points with control relays, auto-clean relay, alarm relay and 4-20mA output.

The TU7685 works using the our TU8182 and TU810 sensors using nephelometric turbidity measuring principle with the light in the infrared spectrum. When combined with the TU8182 or the TU810, the combined turbidity measuring system in accordance with the turbidity measurement methodology as defined using EN 27027 - ISO 7027.

We do offer a sensor to meet United States Environmental Protection Agency standards (USEPA 180.1) which is designed to work with the TU7685. Please get in touch if you wish to learn more about measuring turbidity in accordance with USEPA 180.1 regulations.

The TU7685 is a micro-processor based instrument which allows the turbidity sensor to be calibrated directly from the controller, as well as the range to be adjusted as required.

With a wide range of control options, the TU7685 is a powerful turbidity controller. The  2 x control relays with On/Off functionality can be used to set to High or Low operation.  There is a separate alarm relay which can be configured to energise when the turbidity value is outside of parameter.  In addition there is an industry standard 4-20mA output which is isolated into 600Ω.

Significantly the TU7685 includes an auto-clean relay for use with a compressed air system and suitable dissolved oxygen sensor, such as the TU8182 with autoclean nozzle.  This allows the instrument reading, control relays, alarm relays, and 4-20mA output to be held while water or air are used to clean the lens of the sensor, so preventing residue which may blind or block the sensor from providing accurate readings.

The TU7685 operates from a power supply of either 115 VAC or 230 VAC 50/60Hz.

With a 16 character alphanumeric display, the TU7685 is able display the following ranges:-

Please note NTU is Nephelometric Turbidity Units.

Turbidity RangeTurbidity Resolution
0 - 4.000 NTU 0.001 NTU
0 - 40.00 NTU 0.01 NTU
0 - 400.0 NTU 0.1 NTU
0 - 4000 NTU 1 NTU

The ranges can be changed directly on the TU7685 by following the simple on screen instructions.

TU7685 Turbidity Control Options

The TU7685 turbidity controller has user-configurable set-points which control the TU7685's control relays. These can be set to High or Low operation and have adjustable hysteresis and delay timers.

The control relays are 5 amp non inductive, and offer On/Off functionality for High or Low level operation.  The delay timer can be set from 0-99 seconds and the hysteresis can be set to ± 10% of the set-point value.

The control relays are ideal for feeding a signal back into a control system when the measured Turbidity value is over a desired range.  In addition, they can be used for aerators in aquaculture applications, as well as for controlling valves or pumps, should the turbidity of an effluent or water treatment system exceed a consent to discharge agreement.

In addition to the control relays, there is an alarm relay with 0-25 second delay timer.  The alarm relay can be called when the measured turbidity value exceeds a set parameter which can very useful for triggering a beacon or audible alarm on the measured turbidity falling out of parameter.  Alternatively, the alarm relay can be triggered by one of the control relays, with a delay timer of 0-60 minutes from  the control relay being activated.

Triggering the alarm relay from the control relay is an excellent way of policing a process.  For instance, in a water treatment or effluent treatment application, if the process controlling the outflow is from one of the control relays and if after a delay, the measured Turbidity is still higher than a consent to discharge agreement, an operator can be alerted if the Turbidity value hasn't returned to normal, during the normally expected time period.

TU7685 Turbidity Controller with Auto-Clean

The TU7685 includes another relay designed for auto-clean operation which can work with the TU8182 Turbidity Sensor with auto-clean nozzle.  The relay is designed to control a compressed air system which will blast the lens of the turbidity sensor.  This removes any detritus or build up from the lens of the sensor, allowing extended periods of operation while reducing the requirement for periodic maintenance.

As the auto-clean relay is controlled by the micro-processor measuring the turbidity value, the TU7685 enters Freeze & Hold mode when the autoclean relay is used.  This means that the measured value of the turbidity is frozen when the auto-clean process begins.  It also holds all the control relays, alarm relays, and 4-20mA output during the cleaning cycle.  This prevents any control processes from being called during the cleaning cycle.

TU7685 Dissolved Oxygen 4-20mA Output

The analogue output of the TU7685 can be configured to either 4-20mA or from 0-20mA, as required.  The output is isolated into 600 Ω and is proportional to the measured range of the Turbidity controller, making an excellent output for use with a PLC, digital Chart Recorder, or online Data Logger.

TU7685 Auto-Clean Turbidity Controller Summary

The TU7685 Turbidity Controller is a powerful turbidity instrument which offers excellent accuracy when measuring from as low as 0.001 NTU all the way up to 4000 NTU.

Measuring the turbidity using the nephelometric principle, in accordance with EN 27027 - ISO 7027, when combined with our TU8182 and TU810 (options for using United States Environmental Protection Agency standard USEPA 180.1 is also available) means that the TU7685 offers both precision for process control and environmental monitoring requirements.

With an isolated 4-20mA output, the TU7685 can easily integrate with control equipment and digital Chart Recorders.  The control and alarm relays offer external control of aerators and other associated equipment, to ensure that the turbidity can be accurately controlled or monitored for both environmental and process control applications.

TU7685 Dissolved Oxygen Controller Specifications

  • Specifications


    Model No:- TU7685

    Turbidity Range:- 0 - 4.000 NTU with 0.001 NTU resolution

    Turbidity Range:- 0 - 40.00 NTU with 0.01 NTU resolution

    Turbidity Range:- 0 - 400.0 NTU with 0.1 NTU resolution

    Turbidity Range:- 0 - 4000 NTU with 1 NTU resolution

    Supported Turbidity Sensors (ISO 7027 - EN 27027) :- TU8182 Sumbersible, TU810 inline

    Supported Turbidity Sensors (USEPA 180.1) :- TU820 inline

    Set Points:- 2 Min / Max selectable, contact SPST, 5 Amp inductive

    Action:- On/Off with delay timer of 0-99.9 secs

    Hysteresis:- 0-10% of scale.

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

    Zero:- 0.0 - 10.0 FS

    Slope:- 80-120%

    Mains Supply:- 230/115 volt 50/ 60 Hz.

    Power Consumption:- 5 VA

    Weight:- 850 grams DIN version

    Autoclean:- Manual / Auto + Manual

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

    Designates optional extra.

  • Features


    • Panel mounting turbidity controller complete with auto-clean relay.
    • Precision Dissolved turbidity controller for drinking water quality analysis, water treatment, effluent treatment, aquaculture, and environmental applications in both process and effluent montoring and control.
    • Designed to work with the TU8182 and TU810 turbidity sensors which use the nephelometric turbidity measuring methodology (ISO 7027 - EN 27027), and is also available with a sensor to conform to USEPA 180.1.
    • Full 16 character alphanumeric display showing full soltuion parameters on the home screen and currnet relay states.
    • Two control relays and an alarm relay with easy to configure set-points.
    • Programmable 4-20mA output which is isolated into 600Ω - ideal for connecting to control equipment, PLC's, online data loggers or digital chart recorders.
    • Auto clean relay with freeze and hold functionality means that human intervention for periodic maintenance is reduced.
  • Data Sheets

    Data Sheets


More Information