The difference between thermocouple/temperature transmitter/bimetallic thermometer-

Thermocouples are instruments that convert temperature variables into standardized output signals that can be transmitted. Mainly used for measuring and controlling temperature parameters in industrial processes. A transmitter with sensors usually consists of two parts: the sensor and the signal converter. Sensors are mainly or; Signal converters are mainly composed of measurement units, signal processing and conversion units (due to the standardization of industrial and thermocouple calibration tables, signal converters are also called transmitters when they are independent products). Some transmitters have added display units, and some also have fieldbus functions. If a thermocouple principle transmitter consists of two sensors used to measure temperature differences, there is a given continuous functional relationship between the output signal and the temperature difference. Therefore, it is called a temperature transmitter.
What are the advantages of thermocouples and comparisons?
Thermocouples and bimetallic thermometers are very similar, except that there is a difference in measuring temperature differences. Bimetallic thermometers are more suitable for use in detecting low-temperature conditions in the field. During the measurement process, they can measure the temperature of gas media and liquid vapor from minus 80 degrees Celsius to five hundred degrees Celsius. In industrial high temperatures, thermocouples are mostly used, while in low-temperature environments, bimetallic thermometers are more reasonable to use. The main component of bimetallic thermometers is a multi-layer metal sheet overlapped by one or more metal sheets. Using their different degrees of expansion at different temperatures as the working principle, when one end is heated and expands, the pointer will be driven to rotate, and the working instrument will display it. Provide the corresponding temperature value.
There is a given continuous function relationship (usually a linear function) between the output signal of a temperature transmitter and the temperature variable. Early produced transmitters had a linear function relationship between the output signal and the resistance value (or voltage value) of the temperature sensor. The standardized output signals are mainly DC electrical signals of 0mA~10mA and 4mA~20mA (or 1V~5V). Other standardized output signals with special regulations cannot be excluded. Thermocouple temperature transmitters can be divided into two-wire and four wire systems according to the power supply wiring method. The transmitter comes in both electric unit combination instrument series and miniaturized modular, multi-functional intelligent types. The former does not come with sensors, while the latter two types of transmitters can be easily combined with thermocouples or thermistors to form transmitters with sensors.