The three-valve assembly complements the transmitter, working together to accomplish the task.

The three-valve assembly consists of a valve body, two stop valves, and one balancing valve. The assembly is made up of three valves that communicate with each other. Depending on the role each valve plays in the system, they can be categorized as: the left valve is the high-pressure valve, the right valve is the low-pressure valve, and the middle valve is the balancing valve. The three-valve assembly is used in conjunction with a differential transmitter, its function being to connect or disconnect the positive and negative pressure measuring chambers to the pressure point; or to disconnect or connect the positive and negative pressure measuring chambers.