Brigadoon - An Occasional Corner on the Internet
Designed by Mark Little
Construct Ground Temperature Array (Cont)
Use a tape measure to mark the power wires 10cm, 20cm and 50cm from where the pipe will enter the ground. Carefully strip the insulation at those points so that the power leads from the temperature sensors can be connected to the power wires. After you have attached the wires by soldering or crimp connections, insulate the joints to ensure that the power wires cannot short - use a piece of heat shrink to protect the connection.. Solder the sensor wire for that depth to the output pin of the temperature sensor. When finished, use a piece of tape to hold the temperature sensor in the correct position.
Once the wiring has been completed, apply power to the power wires and check that the outputs of the temperature sensors match the ambient temperature. Remember, the voltage is 2.7315V plus the temperature in Celsius multiplied by 0.01. That is, for a temperature of 25°C, the reading should be 2.7315 + 0.25 = 2.9815V (or as close to that as your voltmeter can read).
Once you are satisfied that the temperature sensors are working correctly, feed a draw wire through the pipe and attach it to end of the wiring furthest from the upper end-cap. Carefully pull the draw wire back out of the pipe, pulling in the wiring loop. When the end cap reaches the top of the pipe, hold the cable loom and the end cap, while screwing the pipe onto the end cap. The objective is to ensure that the wiring loom does not twist while the end cap is attached.
Once end cap is on, trim the end of the cable loom to as close to the length of the pipe as possible and seal the cable ends. Once this has been done, power up the sensor array and check that the temperature sensors still work.
Once the operation of the temperature sensors has been confirmed, screw on the end cap and seal. The unit is now ready to be installed in the ground.