The orifice plate flow meter is installed in the water circuit of the HM 500 trainer. The flow rate measurement is based on the differential pressure method.
The orifice plate narrows the cross-section in the tube. The constriction of the cross-section causes an increase in velocity which results in a measurable differential pressure. A transducer based on variable capacitance (diaphragm method) is used to measure the differential pressure. It is indicated on a display.
Taking the orifice geometry into account, the flow rate can be calculated from the decrease in pressure using Bernoulli’s principle and the Continuity law.