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Digital Thermometers and How They Work

Fundamental to sensing changes in temperature, digital thermometers are an inclusive part of many homes, businesses, and industries. This makes them popular among temperature-measuring equipment, as they provide significant advantages over traditional liquid-based thermometers. Although we may see them in use during our day-to-day lives, continue reading to learn more on how digital thermometers work, alongside their benefits and eventual replacement of traditional thermometers.

Before the advent of digital thermometers, temperature sensing equipment consisted of a glass tube filled with mercury and a standard temperature scale to indicate fluctuations in range, whether that be in degrees Fahrenheit or Celsius. While scientific clinical trials made way for the popularization of classic liquid mercury thermometers between the 17th and 18th century, they also made many aware of the toxicity surrounding mercury and the harmful side-effects it can cause. As mercury is a very dense element, it is one of the only metals that retains its liquid form at room temperature. However, because of its properties, mercury can easily evaporate or find its way into bodies of water, contaminating surrounding air, wildlife, and humans if improperly contained. This was especially an issue with mercury sealed in glass, as accidental drops in commercial and home settings easily led to mercury poisoning from inhaled fumes. This ultimately led to the restriction on sales of mercury thermometers and their phasing out in industrial, laboratory, commercial, and residential settings.

In search of suitable alternatives which mitigate the exposure to liquid mercury and its vapors, the introduction of thermistors in the 1930s provided a clear solution for a dynamic range of temperature sensing applications across the globe. Unlike traditional thermometers which cause internalized liquid to expand or retract to indicate a particular value, modern, digitized thermometers require a sensor and sensor processing equipment to operate. 

To achieve this feature, digital thermometers today are designed to function with a thermocouple, resistance temperature detector (RTD), thermistor, or solid state sensor to produce an analog signal. When changes in temperature are recognized by the sensor, either voltage, current, or resistance oscillate based on their individual analog output signals.

For instance, RTDs are one of the more common choices for constructing a large number of digital thermometers, and they function on the principle that the electrical resistance of a metal changes linearly with temperature. Essentially functioning as an ohmmeter, an instrument used to measure electrical resistance of a circuit, RTDs utilize a small amount of current to “excite” their sensor, simultaneously measuring the amount of voltage present across the sensor. While each sensor is different, it is essential that each thermometer is capable of interpreting and measuring signals created by the sensor.

No matter your industry or application, ASAP Domain 360 can help you source any temperature measurement equipment you need, whether that be a thermistor, thermocouple, an accompanying electromechanical component, and/or more. A proud member of the ASAP Semiconductor family of websites, we are home to over 2 billion new, used, obsolete, and hard-to-find products catering to a broad spectrum of industry verticals. To receive a quote for your comparisons regarding any item(s) of interest, please begin by submitting an Instant RFQ form as listed throughout our website. Providing entities with 24/7x365 customer service assistance, contact us at any time via phone or email for further inquiries; we are available around-the-clock!


November 18, 2022
August 1, 2022


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