Sensors and transmitters are originally concepts of thermal instruments. Sensors convert non electrical physical quantities such as temperature, pressure, liquid level, material, gas characteristics, etc. into electrical signals or directly send physical quantities such as pressure, liquid level, etc. to transmitters.
A transmitter is a signal source that amplifies the weak electrical signals collected by sensors for transmission or activation of control components, or converts non electrical inputs from sensors into electrical signals and amplifies them for remote measurement and control. Analog quantities can also be converted into digital quantities as needed. Sensors and transmitters together form the monitoring signal source for automatic control. Different physical quantities require different sensors and corresponding transmitters. There is also a type of transmitter that does not convert physical quantities into electrical signals, such as the "differential pressure transmitter" of a boiler water level gauge. It sends the condensed water from the lower part of the water level sensor and the upper part of the steam through the instrument tube to both sides of the transmitter's bellows, and uses the differential pressure on both sides of the bellows to drive the mechanical amplification device to indicate the water level with a pointer, which is a remote instrument. Of course, there is also a transmitter that converts electrical analog signals into digital signals. The above is only a conceptual explanation of the difference between sensors and transmitters.
