High-sensitivity NTC resistive sensor for precise, point-source temperature measurements in soil and concrete.
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High-sensitivity NTC resistive sensor for precise, point-source temperature measurements in soil and concrete.
The Geolook Thermistor is a high-precision Resistive (NTC) temperature sensor designed for geotechnical and structural monitoring. Unlike thermocouples which measure a voltage difference, thermistors exhibit a large, predictable change in electrical resistance in response to temperature changes. This sensor is particularly valued for its high sensitivity and resolution over a narrow range, making it the preferred choice for detecting minute thermal fluctuations in soil, rock, and concrete. It is the same high-quality sensing element used for internal temperature compensation in our professional VW Piezometers and Strain Gauges.
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The G89-R400 uses an NTC (Negative Temperature Coefficient) thermistor. This means as the temperature rises, the electrical resistance of the sensor drops. This relationship is non-linear but follows the well-defined Steinhart-Hart equation.
Because the change in resistance is so significant (often thousands of ohms per degree), the sensor is incredibly sensitive. It can detect changes as small as 0.01°C, which is far beyond the capability of most standard industrial thermocouples.
While thermistors are resistive sensors, their high base resistance (e.g., 3000 ohms) means that the resistance of the lead wire has a negligible effect on the reading over moderate distances. For extremely long cable runs (exceeding 500m), we offer 4-wire configurations to mathematically remove lead-wire resistance entirely.
One of the greatest advantages of the Geolook Thermistor is interchangeability. Our sensors are manufactured to such tight tolerances that any G89-R400 can be replaced with another without needing to reprogram the data logger or adjust calibration constants.
This makes them ideal for large-scale deployments where maintenance and simplicity are key project requirements.
For direct burial in soil or concrete, the thermistor bead is encapsulated in a waterproof, thermally-conductive epoxy and housed in a 316-grade stainless steel probe. This ensures the sensor remains protected from the corrosive high-pH environment of wet concrete and the moisture present in deep boreholes.
The G89-R400 uses an NTC (Negative Temperature Coefficient) thermistor. This means as the temperature rises, the electrical resistance of the sensor drops. This relationship is non-linear but follows the well-defined Steinhart-Hart equation.
Because the change in resistance is so significant (often thousands of ohms per degree), the sensor is incredibly sensitive. It can detect changes as small as 0.01°C, which is far beyond the capability of most standard industrial thermocouples.
One of the greatest advantages of the Geolook Thermistor is interchangeability. Our sensors are manufactured to such tight tolerances that any G89-R400 can be replaced with another without needing to reprogram the data logger or adjust calibration constants.
This makes them ideal for large-scale deployments where maintenance and simplicity are key project requirements.
While thermistors are resistive sensors, their high base resistance (e.g., 3000 ohms) means that the resistance of the lead wire has a negligible effect on the reading over moderate distances. For extremely long cable runs (exceeding 500m), we offer 4-wire configurations to mathematically remove lead-wire resistance entirely.
For direct burial in soil or concrete, the thermistor bead is encapsulated in a waterproof, thermally-conductive epoxy and housed in a 316-grade stainless steel probe. This ensures the sensor remains protected from the corrosive high-pH environment of wet concrete and the moisture present in deep boreholes.
We are currently updating the specific model configurations and technical datasheets for this product category.