From the simplicity of Michael Faraday to the complexity of modern electronics, flowmeters have moved with the times and provide an accurate reflection of industrial progress. Most meters now used began, or finished, their main development by 1945.
The Nilometer is a well-documented type of meter alluding to it’s earliest known form. There must have been prototypes of this beforehand, definitely on a less grand scale. Maybe a brick left in a river bed allowed a local observer to draw a conclusion about the state of the water. That would have pre-dated the Nilometer by hundreds of years. What is certain is that they were very visual devices. Someone had to look at the meter itself to know the state of flow.
Leonardo da Vinci, in 1510 or so, observed the eddies trailing the bluff bodies of bridge piers. The frequency of shedding of the vortices is proportional to the flow rate. This physical action is exploited by the Vortex Flowmeter, first commercially available from Eastech in 1969.
In 1738 Bernoulli published Hydrodynamica which described the conservation of energy in flowing fluids. He reasoned that as fluid speeds up it’s kinetic energy increased at the expense of static. He developed an equation for non-compressible fluids. This theory is still applied for one of the oldest methods of flow measurement, orifice plates. The flow rate measured is a function of the pressure drop or loss.
Michael Faraday, in 1832, created an open channel electromagnetic meter at Waterloo Bridge. He used two large metal sheets as electrodes to try and ascertain the flow rate of the Thames. Due to the limitations of instruments at the time he was unsuccessful. By 1930 the principle was adapted for closed pipes and, just after the Atomic Age started, a commercial mag meter was available in the 1950s.
Michael Faraday delivering a Christmas Lecture at the Royal Institution in 1856 / Credits: Wikipedia
Although the first commercial ultrasonic flowmeter was used in the late 1950s earlier patents from the 20s and 30s set the tone. This one, from 1939, specifically references frequency and phase shift.
Coriolis flowmeters seem like the last word in flowmeter techniques but the origins date back to everyone’s friend Gustave Coriolis. Apparently, Napoleon asked Coriolis why cannon balls never went straight. Although this had nothing to do with what we now call the Coriolis effect, it did lead him to research the reasoning. By 1835 he had published research on the effect.
Patents evolved through the 50s and 60s to commercial offerings in the 70s.