Transducers are a type of device that converts varying physical quantities into electrical signals or vice versa. Or, in other words, transducers are devices that convert one form of energy into another. The varying quantities that they can convert include things like brightness, pressure, position, energy, torque, force, position, motion, and heat. Of the many types of transducers manufactured, this article will be taking a closer look at heat transducers, more commonly known as heat sensors. Heat sensors are transducers that generate and use electrical signals to communicate rates of heat change, which operators use to calculate heat flux. Heat flux is the rate per unit time at which heat energy is able to reach and pass through a surface. Heat sensors are implemented in the estimation of fouling on the surface of a boiler, the study of the influence of flames and fire on a surface, and other observational applications that work to increase process efficiency and/or human safety. Examples of commonly used heat sensors include resistance thermometers, thermocouples, thermistors, and silicon bandgap temperature sensors.
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Heat Sensor Types
Of all heat sensors, or temperature sensors, the four most common types of heat sensors are semiconductor based sensors, resistance temperature detectors (RTDs), thermocouples, and negative temperature coefficient (NTC) thermistors. Semiconductor based sensors, used with integrated circuits (ICs), function, for all intents and purposes, as two identical diodes with heat sensitive voltage versus current characteristics. These characteristics allow them to semi-accurately monitor temperature variations. RTDs, or resistance thermometers, consist either of a film or a wire wrapped around a glass or ceramic core. They are highly accurate and measure heat by comparing the resistance of the RTD element against temperature. Thermocouples are made up of two wires, each composed of a different metal, connected at two points. Proportional temperature changes are reflected in the varying voltages of the two connection points. They are incredibly accurate but quite expensive. Finally, NTC thermistors are thermally sensitive resistors that display predictable resistance changes that relate to temperature changes on a large scale. They exhibit high levels of accuracy.
Applications of Heat Sensors
Most often, heat sensors are used for applications in the fields of medical study, agriculture, meteorology, and building construction. In medical studies, heat sensors are used to determine and measure the exchange of heat inside a human body. More plainly, they measure temperature in the human body. In addition to helping individual patients on a case-to-case basis, heat sensors can measure overall average human body heat exchanges. Information such as this is useful beyond the medical field; it can be used in the textile industry to create properly insulated clothing and sleeping bags, as well as immersion suits. In agriculture, heat sensors are buried in the soil of fields to measure heat flux over time. When the information the sensors have recorded is gathered, sensor operators can ascertain with a fair amount of certainty the amount of energy that can be stored in that soil over a corresponding period of time. Next, in meteorology, they help accurately measure heat and help forecast future temperature changes. When used in building construction, heat sensors are placed inside to help builders determine whether or not the walls they have built have yet been well enough insulated. Furthermore, heat sensors can be used to detect and notify people of possible fires. Heat detectors, not to be confused with smoke detectors, sound an alarm in the case of one of two situations. First, some are programmed to sound when temperatures spike suddenly, warning of a fast-growing explosion or fire. Second, others are designed to sound an alarm when surrounding temperatures reach a certain threshold. The latter works when a metal component on the sensor, designed to melt at a certain temperature, melts and triggers the alarm. These types of heat sensors are called rate-of-rise heat detectors and fixed-temperature heat detectors, respectively.
Heat sensors can work in the home, as common thermostats, or in the laboratory, as more complex and precise devices used for scientific research. Typically they work either as contact sensors or non-contact sensors. Contact sensors measure their own internal temperatures after they have matched the heat around them or have achieved thermal equilibrium. Non-contact sensors, on the other hand, measure the heat radiation of the area around them, as agricultural sensors do. In addition, while some heat sensor systems must be checked on-site, many, like remote sensor thermostats, may be operated from afar. Heat sensor systems can also sometimes be improved upon with computerized programming. Unfortunately, heat sensors almost always function with a margin of error, which widens or narrows depending on the sensitivity of an individual device. However, their benefits far outweigh their shortcomings. They make all the difference between a properly functioning system and life or death. To find out more, contact a reputable sensor engineer.