SCIENTIFIC INSTRUMENTS: TEMPERATURE SENSORS
28 February 2022
Temperature sensors are a simple instrument that measures the degree of hotness or coolness and converts it into a readable unit. We all use temperature sensors in our daily olives, be it in the form of thermometers, domestic water heaters, microwaves, or refrigerators.
What is a temperature sensor
- A temperature sensor is a device, typically, a thermocouple or resistance temperature detector, which provides temperature measurement in a readable form through an electrical signal.
- A thermometer is the most basic form of a temperature meter that is used to measure the degree of hotness and coolness.
- Temperature meters are used in the geotechnical field to monitor concrete, structures, soil, water, bridges etc. for structural changes in them due to seasonal variations.
- A thermocouple (T/C) is made from two dissimilar metals that generate an electrical voltage in direct proportion with the change in temperature. An RTD (Resistance Temperature Detector) is a variable resistor that changes its electrical resistance in direct proportion with the change in the temperature in a precise, repeatable, and nearly linear manner.
What do temperature sensors do
- The working of a temperature meter depends upon the voltage across the diode. The temperature change is directly proportional to the diode’s resistance. The cooler the temperature, lesser will be the resistance, and vice-versa.
- The resistance across the diode is measured and converted into readable units of temperature (Fahrenheit, Celsius, Centigrade, etc.) and, displayed in numeric form over readout units. In geotechnical monitoring field, these temperature sensors are used to measure the internal temperature of structures like bridges, dams, buildings, power plants, etc.
What is a temperature sensor used for
- Contact sensors include thermocouples and thermistors because they are in direct contact with the object they are to measure.
- Whereas the non-contact temperature sensors measure the thermal radiation released by the heat source. Such temperature meters are often used in hazardous environments like nuclear power plants or thermal power plants.
- In geotechnical monitoring, temperature sensors measure the heat of hydration in mass concrete structures. They can also be used to monitor the migration of groundwater or seepage. One of the most communal areas where they are used is while curing the concrete because it has to be relatively warm in order to set and cure properly. The seasonal variations cause structural expansion or contraction thereby, changing its overall volume.
How do Temperature Sensors Work
- The basic principle of working of the temperature sensors is the voltage across the diode terminals. If the voltage increases, the temperature also rises, followed by a voltage drop between the transistor terminals of base and emitter in a diode.
- Besides this, Encardio-Rite has a vibrating wire temperature sensor that works on the principle of stress change due to temperature change.
- The vibrating wire temperature meter is designed on the principle that dissimilar metals have a different linear coefficient of expansion with temperature variation.
- It primarily consists of a magnetic, high tensile strength stretched wire, the two ends of which are fixed to any dissimilar metal in a manner that any change in temperature directly affects the tension in the wire and, thus, its natural frequency of vibration.
- The dissimilar metal, in the case of the Encardio-Rite temperature meter, is aluminum (Aluminum has a larger coefficient of thermal expansion than steel.) As the temperature signal is converted into frequency, the same read-out unit which is used for other vibrating wire sensors can also be used for monitoring temperature also.
The change in temperature is sensed by the specially built Encardio-rite vibrating wire sensor and is converted to an electrical signal which is transmitted as a frequency to the read-out unit.
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