Temperature sensors play a crucial role in various industrial applications such as maintenance of the defined temperature for equipment that produces medical drugs, sterilise other devices and/or heat liquids. For likewise applications, responsiveness and precision of the detection circuit may be critical to carry out quality control. A more frequent occurrence is of temperature detection as a division of preventative reliability such as an appliance incapable of performing activities that involve high temperature which puts the entire system at risk of overheating.
This particular risk rises from certain external factors like unsupportive or harsh operating environment or internal aspects like self-heating of the appliances and electronics. Timely detection of the overheating and its causes would allow the system to take preventative action. In all such cases, temperature detection circuits have to be reliable and operable at the temperature that’s required in an industrial setting.
Temperature detection is the basis for all genres of temperature control and compensation. The detection circuit itself tracks ambient temperature, notifies the system of the actual temperature or when the control event should occur; only if it’s a more advanced and intelligent detection circuit. On exceeding the defined high temperature threshold, preventive action is taken by the system to reduce the temperature such as turning on a fan or triggering cold air unit.
Likewise, a temperature detection circuit serves as the heart of compensation function. Take for instance a liquid measuring equipment or system where temperature directly impacts the volume measurement. When taking temperature into account, system becomes compatible to the changing environment factors thus operating consistently and reliably.
- Negative Temperature Coefficient (NTC) Thermistor
Thermally Sensitive Resistor or simply put a ‘thermistor’ exhibits a large, precise and predictable shift in resistance correlated to temperature variations. Then there’s an NTC thermistor which provides sufficiently high resistance at lower temperatures and as the temperature rises, resistance drops quickly. Since an NTC thermistor can experience a large shift in resistance per every degree change in the temperature, readings are reflected faster and with extreme precision.
- Resistance Temperature Detector (RTD)
An RTD can measure temperature via correlating RTD element’s resistance against the temperature. That said, an RTD includes a film for greater precision and a wire wrapped around a glass core or a ceramic. Some of the most accurate RTDs are made up of platinum elements as compared to the economical counterparts that are of nickel or copper however, these elements aren’t too stable or long-lasting. Platinum RTDs on the contrary offer fairly linear results with highest accuracy but cost sufficient.
This particular type of temperature transmitter or sensor consists of two wires made of different metals, joined at two points. The unequal voltage between the two points references proportional shifts in the temperature. Thermocouples are nonlinear which is why they require conversion when intended for temperature compensation and control which is usually achieved by using a lookup table. Though accuracy level is low, they can operate over various and widest range of temperatures which makes them more convenient.
- Semiconductor-based Sensors
A semiconductor-based temperature sensor is carefully positioned on the integrated circuits (ICs). The sensors are effectively two identical diodes with temperature-sensitive characteristics like voltage vs. current which is then used to track temperature change. These provide a linear response but the rate or level of accuracy is lower of the basic class of sensors whereas responsiveness is also slow across narrowest temperature range.