Campbell Scientific 109 109-L Temperature Probe - Page 16

Model 109 Temperature Probe The 109 is held within the radiation shield by a mounting clamp on the bottom plate of the 41303-5A (FIGURE 7-2). Loosen the two mounting clamp screws, and insert the probe through the clamp and into the shield. Tighten the screws to secure the sensor in the shield and route the sensor cable to the instrument enclosure. Secure the cable to the tripod/tower using cable ties. 7.4 Water Temperature Installation 109 probes can be submerged to 15 m (50 ft) or 21 psi. The 109 is not weighted, so a weighting system should be added, or the probe secured to a fixed or submerged object such as a piling. 7.5 Soil Temperature Installation The 109 tends to measure the average temperature over its length, so it should generally be buried such that the measurement tip is horizontal to the soil surface at the desired depth. One or two coils of cable should also be buried in a shallow installation. Burial of some cable mitigates the effect of solar heating of the above ground cable on the temperature measurement. Placement of the cable inside a rugged conduit may be necessary for long cable runs, especially in locations subject to digging, mowing, traffic, use of power tools, or lightning strikes. The maximum burial depth for soil that could become saturated with water is dictated by the maximum water pressure allowed for the sensor, which is 21 psi. 8. Operation 8.1 Sensor Schematic FIGURE 8-1. 109 Thermistor Probe Schematic 10