Vacuum (or compound) pressure transmitters measure both negative and positive pressure. They are employed in HVAC and refrigeration systems, industrial vacuum pumps, process control, environmental monitoring, and scientific research. In HVAC and refrigeration, they monitor refrigerant pressures, ensure proper pump operation, and regulate pressure levels. In industrial vacuum pumps, they measure the vacuum created by pumps, prevent cavitation, and optimize pump performance. In process control, they monitor pressure of pneumatic actuators, gasses in reactors, and other materials. For environmental monitoring, they track air pressure at different altitudes and assess atmospheric pressure changes. In scientific research, they monitor vacuum chamber pressure, atmospheric pressure fluctuations, and gas dynamics in flow systems.