Niphargus: A silicon band-gap sensor temperature logger for high-precision environmental monitoring

• We developed a temperature data logger ‘Niphargus” based on a monolithic band-gap sensor.
• The logger is built to log temperature for several years in harsh environmental conditions.
• The logger has a resolution of 0.0078 °C and an initial absolute accuracy of 0.5 or 0.25 °C than can be improved through calibration.
• We have deployed successfully the Niphargus logger to monitor a cave system in Han sur Lesse and a water stream near the town of Spa (Belgium).

A temperature logger, named “Niphargus”, was developed at the Geological Survey of Belgium to monitor temperature of local natural processes. It has a sensitivity of the order of a few hundredths of degrees on temperature variability in open air, caves, soils and river environment. The newly developed instrument uses a state-of-the-art band-gap silicon temperature sensor with integrated digital output. This sensor reduces the risk of drift associated with thermistor-based sensing devices, especially in humid environments. The Niphargus is designed to be highly reliable, low-cost and powered by a single lithium cell with up to several years autonomy, depending on the sampling rate and environmental conditions. A batch of Niphargus loggers was also compared to a precision thermistor to assess absolute temperature accuracy. Further characterization came from two field case studies in Belgium: monitoring of a mineralized water stream near the town of Spa and air temperature monitoring inside Han-sur-Lesse cave.

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