The Birth of the Electro-magnetic Flow Meter

The principle originally applied is that of the “Hall Effect”. The
Hall effect refers to the potential difference (Hall voltage)
on the opposite sides of an electrical conductor through which an electric current is flowing, created by a magnetic field applied perpendicular to the current. Edwin Hall discovered this effect in 1879.

Electronically manipulating this potential the rate of flow and the total flow of the solution can be attained. One of the more important advantages of this type of device or meter is that it provides no more restriction to the flow than an equivalent length of pipe. The original design is generally described as follows.

An electromagnet was designed such that when the solution of interest was passed through the flux field (at right angles) of the magnet a current of measurable value was attained. A length stainless steel pipe insulated from the solution by lining the inside of the pipe with a sleeve of glass re-enforced Teflon â was the housing for a set of stainless steel diametrically opposed electrodes. These were installed in the pipe at the diameter of the pipe.

These electrodes were insulated from the pipe wall but came into contact with the solution. Now the voltage drop across the solution could be measured. This voltage drop was compared to a reference voltage and any difference was sent to a circular chart recorder via an amplifier. The chart reorder displayed the rate of flow. If required, a “Ball and Disc” integrator using a linear cam was used to display total flow on mechanical counters.

The models of these meters were large and the magnets were quite heavy and the magnet’s size was determined by the minimum flow rate of the application. Weights of 2 pounds to several hundred pounds were used. The electronics consisted of two “relay racks” housing the power supplies, amplifiers, circular chart recorders and the “ball & disc integrators” cam-coupled to “Veeder-Root” counters. The accuracy of these early units was rated as a percentage of full scale. Ideally the solution had to have a conductivity of less than 100,000 micromhos and preferably laminar flow for maximum accuracy.

The original patent for using the “HALL” principle for measuring the blood flow in animals was held by Dr. Kolin of the University of Chicago. A license was obtained by Bowser, Incorporated, of Ft Wayne, Indiana-circa 1951. The Advanced Research and Development Department of Bowser, which consisted of four individuals – one PHD in engineering, one Engineer and three Electro-mechanical technicians, of which the author was one, designed, fabricated, tested and installed various models at several companies. Some but not all companies are listed below:

1. R.T French Rochester, New York – Measuring the flow of 129 grain vinegar and mustard.
2. Argonne Nat’l Labs of Chicago – Measuring the flow of heavy water at 20,000 gallons per minute.
3. The Standard Oil Co. of Richmond, Ca – Measuring the flow of sulfuric acid.
4. Kraft Foods of Beaver Dam, Wisconsin – Measuring flow rate and quantity of milk as delivered by and from stainless steel tankers.
5. Exchange Lemon Products of Corona, CA – Measuring the rate of flow and quantity of juices obtained from processed lemons and other fruit.

Sometime after 1953 Bowser sold all rights to the Foxboro Corp of Massachusetts and the Bowser endeavor was disbanded.

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