An old fashioned way to measure liquid flow, probably used by the Romans B.C., is to observe the level change over time in a reservoir or tank. The volume change gives the total flow. Dividing the volume change by the time to change yields the flow rate. A true displacement flowmeter.

Many otherwise difficult liquids can be measured this way. Waste water lift stations are a popular application. Municipal or industrial standpipes are another. Steam condensate receivers are a third.

These applications experience level changes while being filled or emptied by the ON/OFF operation of pumps controlled by level sensors.

Unlike Roman times, now computer chips are used to do the timing and calculations required to make this type of displacement flowmeter a reality. Additional functions are easily included.

Benefits include:

• no piping modifications (electrical installation only)
• no parts in contact with aggressive fluids
• long term accuracy based on physical dimensions and time