Testing the Conductance of the Probes
It is important that the encasement for our temperature sensors allow for heat to be easily transferred through so that the sensors can have extremely accurate readings. This is because the soils is being warmed 4 degrees Celsius higher than the current temperature of the soil. In order to accurately measure how the change in temperature effects the soil we need to have accurate temperature readings from the temperature sensors. The probes for the temperature sensors are galvanized steel with thin walls in order to allow heat to be transferred through. The temperature sensor itself is inside the probe surrounded by heat conductive epoxy. Before we created the 50 temperature probes needed for this project, will tested a prototype of the sensor at the Marine Embedded Systems Hui (MESH) lab. Big thanks to Dr. Brian Glazer and Stanley Lio for their help in designing and setting up this conductance test!
MISSING
Figure 1: First look at the temperature probe prototype.
We placed the metal probe in a water bath tank used for measuring temperature gradients. This was important for measuring the temperature gradient along the probe, to make sure it is conducting heat properly. Next we placed three temperature sensors (white casings) at the top middle and bottom of the probe to measure the temperature gradient of the probe. Then we placed a temperature sensor inside the probe and snaked it all the way to the bottom of the probe so it would correspond with the reading for the bottom temperature sensor (see Figure 2).
Figure 2: The water bath set up for the probe conductance test (probe is on far right inside blue box). Three temperature senors on the outside of the probe (white), one temperature sensor on the inside of the probe.
If the bottom temperature sensor had the same reading (within 0.01 degree Celsius) as the internal temperature sensor then we could assume there is adequate conductance of heat for the metal probe. We found however that the temperature outside of the probe was 1 degree Celsius cooler than the temperature sensor reading inside the probe. This meant that the conductance for the metal probe is poor and will not work for this experiment.
Figure 3: Graph and real time data reading from the Python script of the experimental set up. The bottom sensor in green is over a degree lower than the internal sensor in blue.
Needing to come up with a new idea for encasing the temperature sensors we devised waterproofing the temperature sensors themselves in a 3D printed casing and then burying them in the soil at their desired depth (the 5 different depths that will correspond to the gas wells). Since Hawaii has little large organisms in the soil that will be able to move the sensors via digging or chewing (think gophers and rabbits) this new set up should be able to stay in place and allow use to get the proper temperature reading from each sensor.
