This section provides overview, applications, and principles of temperature sensors. Also, please take a look at the list of 66 temperature sensor manufacturers and their company rankings.
A temperature alarm is a device that sounds an alarm when the temperature detected by a temperature sensor rises above or below a set temperature.
Thermocouples are used as temperature sensors, which are made by bringing the tips of two different types of metal wires into contact to form a single circuit, using the Seebeck effect. A voltage is generated when there is a temperature difference between the contact points of the two types of metal wires.
Resistance Temperature Detectors (RTDs) using platinum (Pt), nickel (Ni), or copper (Cu) are also commonly used, taking advantage of the electrical resistance of metals and metal oxides that increases with increasing temperature.
Temperature alarms are often used to send out alarms and shut down equipment to prevent overheating of heaters.
They are also used to alert people to abnormal temperatures in factories, plastic greenhouses, and refrigerators by means of lamps, sounds, and buzzers.
Alarms utilizing thermocouples, which have a long life span, high heat resistance, and high mechanical strength, are most commonly used for both domestic and industrial applications.
In addition, alarms using platinum resistance thermometers, which have a wide range of temperatures to be used, are used for research and industrial applications.
The principle and structure of thermocouple temperature alarms are described below.
A minute voltage is generated in response to the temperature difference (Th-Tc) between the cold junction (Tc) of the connector part and the warm junction (Th) of the two types of metal wire contacts.
Incorporate a temperature sensor that outputs an absolute voltage corresponding to the temperature (Tc) of the cold contact at the connector section.
The temperature of the measured object (Th) is measured by combining the minute voltage resulting from the temperature difference (Th-Tc) and the voltage corresponding to the temperature (Tc) of the cold junction.
Furthermore, the sensor is used as an alarm by incorporating electronic components that emit an alarm signal when the voltage reaches a voltage, indicating the set temperature.
The principle and structure of a resistance thermometer temperature alarm are described below.
To measure temperature using a resistance thermometer, a certain current is applied to the resistance thermometer and the voltage at both ends is measured.
When the voltage becomes equal to the set temperature, an electronic component that outputs an alarm signal is built in and used as an alarm.
A 2-wire circuit with two leads for the resistance thermometer is affected by the resistance of the wires, so a 3-wire or 4-wire circuit may be used.
*Including some distributors, etc.
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