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Construct Ground Temperature Array
Designed by Mark Little
Now that the sensors have been built and calibrated, it is time to to put things together into the array module that will be put into the ground. The first decision is how to bring the cable into the pipe through the end cap. Ideally, a socket should be mounted in the end cap. This allows the array to be installed without the cable getting in the way and it is easier to replace the cable if it gets damaged later.
However, in some cass, this is not practical, so an alternative is to use a waterproof gland to allow the cable to directly enter the pipe holding the sensors with perhaps a waterproof connector a short way along the cable exiting the pipe. For Australian constructors, waterproof glands can be obtained from many suppliers, such as Jaycar Electronics where the electronic components can be obtained, although this example will use an 8-pin mini-DIN plug and socket.
The 8-pin mini-DIN plug and socket are being used because I was able to obtain them very cheaply. They suffer from two disadvantages: (1) They are not weatherproof and they will need to be weatherproofed after installation and testing; (2) The socket is designed to be soldered into a Printed Circuit Board (PCB) to hold it in place. Since this connector is going to be mounted in the end cap of the pipe holding the temperature sensors, a fixing method will need to be developed.
Pin Wire Colour (nominal) Length Function
1 Yellow 10cm Data
2     Not Connected
3 Black 10cm Power and Digital Earth Connection.
4     Not Connected
5 Red 10cm +5V Power Rail
6     Not Connected
7     Not Connected
8     Not Connected
Take the end cap and mark the center of the cap and drill a hole just smaller that the diameter of the DIN socket. Adjust the size of the hole so that the connector can be firmly pressed into the cap (but don't do it yet!).
Solder wires to the socket pins according to the wiring list below. Refer to the Analogue Temperature Construction for more information.
Sensor Cable Length Function
1   Temperature at 10cm depth
2   Temperature at 20cm depth
3   Temperature at 50cm depth
4   Temperature at 100cm depth
Since the 60cm sensor tube is 10cm longer than the 50cm sensor depth, and the 120cm sensor tube is 20cm longer than the 100cm sensor depth, the junction between the wires connected to the connector and the cables to the sensor can be located at or above ground level,above the water level, even if the tube floods for some reason.

To make this easier, the sensor cables should be cut to the following lengths  and the send stripped so that they can be joined together with the wires from the connector, and then hang to the correct depth.
Construction Design Under Development