With a constriction type, differential head flow meter, which of the following would be an example of a primary device?

Correct Answer: Option D — Orifice plate or venturi tube

In differential head flow measurement, the primary device is the physical element installed in the piping to create a pressure drop, such as an orifice plate, venturi tube, or flow nozzle. The transmitter and manometer are secondary devices used to measure and convert that pressure differential into a signal.