What principle does a basic differential pressure transmitter operate on when measuring fluid flow?

A basic differential pressure transmitter measures fluid flow by utilizing the principle of pressure differential caused by the fluid itself. When there is flow through a pipe or duct, the fluid experiences a pressure drop across a constriction or orifice. This difference in pressure can be converted into an electrical signal that is proportional to the flow rate.

The correct answer highlights that the output signal variance is directly related to the flow rate. As the flow increases, the differential pressure also changes, resulting in a corresponding change in the output signal. This relationship enables operators to monitor and control flow effectively by interpreting the electrical signal generated by the transmitter.

Understanding this principle is essential because it underlines how flow measurement is reliant on pressure differences rather than other factors such as fluid density, temperature fluctuations, or variations in input signals, which are not the primary mechanisms involved in the operation of a differential pressure transmitter.