The 108 is a rugged, accurate probe that measures temperature of air, soil, or water from -5° to +95°C. It easily interfaces with most Campbell Scientific dataloggers and can be used in a variety of applications.
The 108 consists of a thermistor encapsulated in an epoxy-filled aluminum housing. The housing protects the thermistor. allowing you to bury the probe in soil or submerge it in water.
|Sensor Description||BetaTherm 100K6A1IA Thermistor|
|Tolerance||±0.2°C (over 0° to 70°C range)|
|Temperature Measurement Range||-5° to +95°C|
|Steinhart-Hart Equation Error||≤ ±0.01°C over measurement range (CRBasic data loggers only)|
|Polynomial Linearization Error||Typically < ±0.5°C over -5° to 90°C range (Edlog data loggers only)|
|Time Constant in Air||30 to 60 s (in a wind speed of 5 m s-1)|
|Maximum Submersion Depth||15 m (50 ft)|
|Maximum Cable Length||305 m (1000 ft)|
|Probe Diameter||0.76 cm (0.3 in.)|
|Probe Length||10.4 cm (4.1 in.)|
|Weight||136 g (5 oz) with 3.05 m (10 ft) cable|
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
One single-ended channel per probe is required; an excitation channel can be shared by several probes.
When exposed to sunlight, the 108 should be housed in a 41303-5A, 41303-5B, or RAD06 6-plate radiation shield. The louvered construction of these radiation shields allows air to pass freely through the shield, thereby keeping the sensor at or near ambient temperature. The shields’ white color reflects solar radiation.
The RAD06 uses a double-louvered design that offers improved sensor protection from driving rain, snow, insect intrusion and has lower self-heating in bright sunlight combined with higher temperatures (> 24°C [~75°F]) and low wind speeds (< 2 m/s [~4.5 mph]), giving a better measurement.
The 41303-5A and RAD06 attach to a crossarm, mast, or user-supplied pipe with a 2.5 to 5.3 cm (1.0 in to 2.1 in.) outer diameter. The 41303-5B attaches to a CM500-series pole or a user-supplied pole with a 5.1 cm (2.4 in.) outer diameter.
The 108 is suitable for shallow burial only. Placement of the sensor’s cable inside a rugged conduit may be advisable for long cable runs—especially in locations subject to digging, mowing, traffic, use of power tools, or lightning strikes.
The sensor can be submerged to 15 m (50 ft) or 21 psi. Please note that the 108 is not weighted. Therefore, the installer should either add a weighting system or secure the sensor to a fixed, submerged object, such as a piling.
To measure large numbers of probes, the AM16/32B multiplexer is recommended.
Number of FAQs related to 108-L: 5
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The thermistor is located approximately 3 mm (0.125 in.) back from the probe tip.
Note the difference between calibration and a field check. Calibration cannot be done in the field, as it requires an experienced technician and specialized equipment.
Field checks of measurements can be done to determine if the data make sense with the real-world conditions. Follow these steps to field check a sensor:
The sensor/probe consists of a non-linear thermistor configured with a precision resistor in a half-bridge circuit, as shown in the product’s manual:
To measure the sensor/probe, the measurement device has to provide a precision excitation voltage (Campbell Scientific dataloggers use 2000 mV), measure the voltage across the precision resistor, determine the thermistor resistance (Ohm's law), and convert the resistance to temperature using the Steinhart-Hart equation.
The Steinhart-Hart equation is 1/T = A + Bln(R) + C(ln(R))3 where:
For the 107-L, 107-LC, 108-L, and 108-LC, the following are the coefficients for the Steinhart-Hart equation:
For the 109-L, the following are the coefficients for the Steinhart-Hart equation:
Most Campbell Scientific sensors are available as an –L, which indicates a user-specified cable length. If a sensor is listed as an –LX model (where “X” is some other character), that sensor’s cable has a user-specified length, but it terminates with a specific connector for a unique system:
If a sensor does not have an –L or other –LX designation after the main model number, the sensor has a set cable length. The cable length is listed at the end of the Description field on the product’s Ordering tab. For example, the 034B-ET model has a description of “Met One Wind Set for ET Station, 67 inch Cable.” Products with a set cable length terminate, as a default, with pigtails.
If a cable terminates with a special connector for a unique system, the end of the model number designates which system. For example, the 034B-ET model designates the sensor as a 034B for an ET107 system.
Many Campbell Scientific sensors are available with different cable termination options. These options include the following:
Note: The availability of cable termination options varies by sensor. For example, sensors may have none, two, or several options to choose from. If a desired option is not listed for a specific sensor, contact an application engineer at Campbell Scientific for assistance.