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(Sensor Only)

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3.1 Installation

The D-Opto can be mounted in any orientation; however it is recommended that the optical window face away from direct sunlight.

The body can be clamped in position; however avoid using excessive force. The cable should be secured along a solid structure to prevent it trailing in the water.

D-Opto wiring configuration

3.2 Communication

SDI-12 (Serial-Digital Interface Standard) is a single wire communication protocol which was developed principally for use in low power micro-processor based sensors, such as those typically used in environmental monitoring. The protocol is widely used, and most data loggers have SDI-12 communication capability.

The SDI-12 protocol provides a simple yet reliable means of transferring data between the data logger and the instrument. Multiple instruments can share a single communication cable though the use of addressing, whereby each sensor is given a unique address, and only responds when its address is associated with a command, therefore ignoring all other commands.

The D-Opto SDI-12 address is set in the settings window in D-OptoCom software

There are two commands that can be used to request that the D-Opto take a measurement; these are “M!” and “M1!” (see manuals Appendix 2 for examples of how to program a Campbell data logger to interface with the D-Opto).
The M! Command is used where a single measurement is required. When the D-Opto receives the M! Command, the optical circuitry in the D-Opto is powered up and after a stabilization period of 5 seconds, a measurement is made and the values returned to the data logger; the optical circuitry is then powered down.

The M1! Command is used where a continuous burst measurement is required.
When the D-Opto receives the M1! Command, the optical circuitry is powered up.
After 5 seconds a measurement is made and the values are returned to the data logger. The optical circuitry remains powered up. Another M1! Command can be issued by the data logger and will be responded to immediately by the D-Opto without a 5 second delay. The maximum sampling rate is approximately one measurement per second. The optical circuitry remains powered up until no relevant commands are received for 6 seconds.

Three data values are returned by the D-Opto, in the following order;

1. Temperature (°C)
2. Dissolved oxygen (% Saturation)
3. Dissolved oxygen (ppm)