text: what is a pressure transmitter?   pressure transmitters are used in research and development, process control, and factory automation to tell a control system or operator what the pressure is at the sensor location.  a "transmitter" tells you the pressure reading is converted to some type of signal that may be "transmitted" to another location.  the simplest transmitters only have a switch contact that closes or opens at a certain pressure point.  for instance, a spring-operated diaphragm connected to a variable resistor will sense the oil pressure in your car engine, and send a different voltage depending on the pressure.  the characteristic of the voltage level to pressure ratio is known in the sensor design, so the computer knows how to interpret the voltage.    transmitters have all kinds of formats these days.  common units output a current (4-20ma) or a voltage (all ranges: 0-5, 1-5, 0-10, etc.)  and are customizable.  with the advent of the cheap microcontroller, however, sensors are more flexible.  they can output a data stream with rs232 or rs485 (addressable), or nowadays the sensors can be networked with cat-5 cable and internet protocol.  this is great when you have many sensors reporting to a central controller over long distances.