D-Opto Optical Dissolved Oxygen Sensor
D-Opto SDI-12 Optical DO Sensor
The D-Opto is an instrument designed for measuring dissolved oxygen concentrations in liquids. The instrument uses field proven solid state optical sensing technology that is highly stable over long periods of time, even in harsh conditions. The D-Opto has extremely low power requirements, and outputs the data in SDI-12 format, making it ideal for incorporation into remote environmental monitoring installations. Percent saturation values generated by the D-Opto are the percentage saturation that would occur if the measured liquid were saturated with air under a standard barometric pressure of 1013 mBar at the same temperature.
The D-Opto sensing element utilises fluorescence to measure dissolved oxygen. The basic principle involves subjecting a fluorescing compound to a fixed wavelength of light. When the light source is removed, the compound emits a fluorescence, the intensity of which is dependent on the oxygen levels present in the surrounding water. Ruthenium is used as the fluorescing compound in the D-Opto. An extremely stable electronic circuit is used to excite the ruthenium, and then measure the intensity of fluorescence. As a result, the D-Opto should provide accurate dissolved oxygen measurements over long periods of time without the need for re-calibration.
Unlike conventional polarographic dissolved oxygen sensors, the optical method does not consume oxygen. Consequently the measurement of dissolved oxygen by the D-Opto is unaffected by water flow. Similarly the D-Opto does not utilise a membrane or any other consumables, thus minimising servicing requirements.
The D-Opto sensor is currently available with s SDI-12 interface, but other interfaces are under development.

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D-Opto Optical Dissolved Oxygen Logger
The D-OptoLogger is a fully self contained dissolved oxygen logger, incorporating an Optical DO sensor, battery, and low power data logger in a rugged compact underwater housing. The D-OptoLogger uses a field-proven solid-state optical sensing system to measure dissolved oxygen that is highly stable over long periods of time, even in harsh conditions. The data is stored onboard in non-volatile memory. The D-OptoLogger is setup, and data offloaded, using simple Windows based software, supplied with the instrument.
Product Description: Optical Sensor Technology
Unlike conventional dissolved oxygen sensors, the D-OptoLogger sensing element utilizes fluorescence to measure dissolved oxygen. The basic principle involves subjecting a fluorescing compound (ruthenium) to a fixed wavelength of light. When the light source is removed, the compound emits a fluorescence, the intensity of which is dependent on the oxygen levels present in the surrounding water. An extremely stable electronic circuit has been designed to firstly excite the ruthenium, and then measure the intensity of the resulting fluorescence. Using this circuitry, the D-OptoLogger provides accurate dissolved oxygen measurements over long periods of time (many months) without re-calibration.

Unlike conventional polargraphic dissolved oxygen sensors, the optical method does not consume oxygen. Consequently the measurement of dissolved oxygen by the D-OptoLogger is unaffected by water movement.

The DoptoLogger does not utilize a membrane or any other consumables, thus minimizing servicing requirements.

Operation:
The D-OptoLogger is supplied with a communication cable. This cable has a 9 pin serial plug on one end, and a 3.5mm jack plug on the other end.

The 9 pin plug is plugged into the serial plug on the PC. If the PC does not have a serial port, a USB to serial adaptor can be used. This adaptor plugs into the USB port on the PC, and has a serial port that the communication cable 9 pin plug can be plugged into.

The jack plug on the cable is plugged into the communication socket. This is accessed by removing the D-OptoLogger end cap.

Logging Endurance:
Circular or Wrap Around logging options.

If the D-OptoLogger is set to circular memory, the possible effective length of deployment will be limited by the life of the batteries. This will depend on the logging interval, and the quality of batteries used. Typically the power endurance should exceed 30 days for all logging intervals.

If the D-OptoLogger memory mode is set to stop logging when memory is full, the memory endurance is:

Logging Interval - Memory Endurance
(minutes)             (days)
 1                           3
 5                          15
10                          31
15                          46
30                          93
60                         186