What is analog transmitter?

a device used to convert a process measurement (i.e. temp, pressure, level) to an analog value which is typically 4-20 mA of electrical current. For instance you need to measure the temperature of water in a pipe. An RTD or a thermocouple will be attached in a way that it can sense the temp. The transmitter will read the temp from which ever you use and convert it into milliamps. So if the range of the transmitter is 0-100 degrees F at 0 degrees the transmitter will output 4mA at 100 degrees it will output 20mA. also 50 dgrees would be 12mA.