A Note on Remote Temperature Measurements with DS18B20 Digital Sensors
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Digital temperature sensors provide an attractive means to conveniently record ice and water temperatures in remote locations. Unlike conventional analogue techniques, a digital sensor performs a physical measurement, interprets its result in terms of temperature and transmits that result to a logger or display system in digital form. Processing of digital signals is comparatively robust and cheap. Custom calibration may be applied to increase measurement accuracy. A popular example of a digital temperature sensor is the Maxim Integrated DS18B20, which is readily available as a bare sensor in a standard transistor casing, or from third-part providers as a probe with the sensor encased in a waterproofed metal sleeve. We found that the quality of water protection of the probes varies widely, and that bare sensors and sensors in probes offered by most third-party providers (i.e. not by official distributors) are almost always clones, i.e. not produced by Maxim Integrated. We summarize in this paper the spectrum of counterfeit sensors currently available and how they differ from authentic parts and specifications in the Maxim Integrated data sheet. Currently sold sensors are grouped into 7 families, 6 of them representing counterfeits. Awareness of the prevalence and characteristics of counterfeit sensors will help avoid surprises during costly experimental field work.