After sensing the pressure drop, what does the differential pressure transmitter produce?

• A. A voltage reading
• B. A resistance value
• C. A temperature reading
• D. A current signal proportional to the pressure drop

Answer: (D)

A differential pressure transmitter converts the mechanical difference across a sensing diaphragm into an electrical signal that a controller can read. The transmitter’s output is a current in a loop that is proportional to the pressure difference, commonly 4-20 mA, where 4 mA represents near-zero differential and 20 mA represents full-scale differential. This current loop is favored because it stays accurate over long cable runs and under varying load, making it reliable for process control. Other output forms like voltage, resistance, or a direct temperature reading aren’t the standard way a DP transmitter communicates its measured pressure difference.