Dissolved Oxygen Controller with Auto-Clean

The OD7685 Dissolved Oxygen Controller is an auto-ranging instrument ensuring the appropriate range is visible automatically even as the measure dissolved oxygen value changes.

OD7685 Auto-Clean Dissolved Oxygen Controller Introduction

The OD7685 Dissolved Oxygen controller is designed to offer accurate Dissolved Oxygen measurements in both environmental applications and in industrial processes such as boiler feed water and where the levels of dissolved oxygen are critical to process or industrial performance.

The OD7685 is a micro-processor based instrument and as such features accurate measurement of dissolved oxygen and a range of output options for the use with control equipment. 

With a wide range of control options, the OD7685 is a powerful dissolved oxygen 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 dissolved oxygen value is outside of parameter. In addition there is a programmable industry standard 4-20mA output which is isolated into 600Ω.

Significantly the OD7685 includes an auto-clean relay for use with a compressed air system and suitable dissolved oxygen sensor, such as the Polarographic Membrane Cell DES-1 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 membrane of the sensor, preventing residue which may blind or block the sensor from providing accurate readings.

The OD7685 operates from a power supply of either 115 VAC or 230 VAC 50/60Hz.

With a 16 character alphanumeric display, the OD7685 is able display the following ranges:-

OD7685 Dissolved Oxygen Controller with Automatic Compensation

The OD7685 dissolved oxygen controller is a very sophisticated instrument offering compensation for a number of external environmental factors including:-

• Automatic Temperature Compensation
• Automatic Thermo-resistance Compensation
• (Optional) Automatic Barometric Temperature Compensation
• (Optional) Automatic Relative Humidity Compensation
• Automatic Salinity Compensation (0 - 60'000 ppm)

The Automatic Salinity compensation allows the instrument to adjust the concentration measurement (mg/L) according to the user input of the PPT of chloride concentration of the sample. The automatic temperature compensation with a user selectable co-efficient (default setting 2.3%) between 0-4.00 % per °C.

In addition to using the conversion co-efficient's, the OD7685 includes a set of preprogrammed co-efficient tables within the micro-processor, to offer increased precision on automatically compensated values. Please contact us if you require any specific information about this element of the operation of the OD7685 dissolved oxygen controller.

OD7685 Dissolved Oxygen 4-20mA Output

The analogue output of the OD7685 can be configured to either 4-20mA or from 0-20mA as required. The output can be also be set proportionally or inverted to increase granularity or give proportional control to a compatible control device or aerator.

The 4-20mA can be scaled across 2 values within a range. So for instance, in the measuring range of the 0-200.0% saturation or concentration of 0-20.00 mg/L or ppm, the range could be 50-100% saturation or 10ppm-20ppm concentration.

The 4-20mA output is isolated to 600Ω and is designed to work with control equipment; PLC's; online Data Loggers, Chart Recorders or any other device that takes an industry standard 4-20mA signal.

OD7685 Dissolved Oxygen Controller Set-points and Relays

The OD7685 Dissolved Oxygen controller has 2 x Set-points which correspond to 2 x control relays offering On/Off control. These two control relays are 5 amp non-inductive and can be independently set from one another.

The control relays are also fitted with a user-selectable delay timer where the time can be set from 0-25 seconds as required. In addition the two control relays have an adjustable hysteresis value from ±10% of the set-point.

The OD7685 also includes an alarm relay which can be triggered to activate when the measured dissolved oxygen value is outside of parameter, with a delay timer of 1 minute. In addition, the alarm relay can be triggered following on from set-point 1 or set-point 2, with an adjustable delay from 0-60 mins activation.

OD7685 Auto-Clean Dissolved Oxygen Controller Summary

The OD7685 Dissolved Oxygen Controller is a powerful dissolved oxygen instrument offering a variety of accurate online dissolved oxygen measurements including percentage saturation, concentration and partial pressure.

With an isolated and programmable 4-20mA output, the OD7685 can easily integrate with control equipment and digital Chart Recorders easily. The control and alarm relays offer external control of aerators and other associated equipment to ensure that the dissolved oxygen can be accurately controlled or monitored for both environmental and process control applications.