Groundbreaking Weston Instruments Recognized With an IEEE Milestone

The first portable voltmeter and a shunt for measuring large currents were honored

7 November 2016

The late 1800s marked the dawn of electricity’s widespread use in the United States. Power companies were building distribution systems to supply electricity to industrial and residential customers. Incandescent lightbulbs were introduced, making electric lighting an economical competitor to gas lighting. This rise in popularity required instruments to quantify electricity. The efficiency of motors and generators needed to be measured. Voltage and current needed to be measured and controlled. And for billing purposes, utilities wanted to measure how much electricity each customer was using.

That’s where Edward Weston, an English-born American chemist, came in. In 1888 he founded Weston Electrical Instrument Corp. in Newark, N.J. The company introduced a voltmeter for measuring the electrical potential difference between two points in an electric circuit and, among other innovations, a shunt for measuring large currents.

Weston’s inventions were recognized in September with an IEEE Milestone. Administered by the IEEE History Center and supported by donors, the IEEE Milestone program recognizes outstanding technical developments around the world.

MEASURING UP

In 1879, as electricity became more and more popular, Thomas Edison attempted to measure customers’ electricity usage so that power companies could bill them. He tried a chemical meter that used current to plate zinc onto electrodes. By weighing the electrodes to learn how much zinc had accumulated, Edison’s company could calculate how much electricity was used. The meter, however, was inefficient and error-prone.

In 1888 Weston developed the first accurate and portable analog voltmeter, an instrument that could measure the voltage between two points in an electric circuit. He was improving upon an early galvanometer, an electromechanical instrument for detecting and measuring electric current.

In a voltmeter, a small pivoting coil of wire is attached to a thin pointer that moves over a calibrated scale. When a direct current flows through the coil, the coil generates a magnetic field, which acts against a permanent magnet. The coil twists, pushing against a spring, and moves the pointer.

That voltmeter design paved the way for the ammeter (which measures electric current) and the wattmeter (which measures a circuit’s electric power in watts).

Weston also invented two metal alloys, constantan and Manganin, whose resistances are constant over a wide range of temperatures. Both lightweight materials were incorporated into the meters’ magnetic pointers and internal springs.

In 1893 Weston invented a shunt that measured large current and contained multiple calibrated current scales in a single instrument. Previous shunts relied on heavy, expensive bars of copper; Weston’s, which used Manganin instead, made them obsolete.

Weston’s instruments soon became the gold standard, adopted by nearly every utility around the world.

THE MAN BEHIND THE METERS

Born in England in 1850, Weston originally studied medicine but soon became interested in chemistry. He moved in 1870 to New York City, where he worked for two years as a chemist and electrician before establishing a nickel-plating business in 1872. That business was incorporated as the Weston Co. in 1877, and in 1881 was consolidated with the U.S. Electric Light Co., where Weston served as electrician until 1888. During that time, he was contracted to illuminate the Brooklyn Bridge, which opened in 1883.

After founding the Weston Electrical Instrument Corp. in 1888 in Newark, he served as its president until 1924. He was also president from 1888 to 1889 of the American Institute of Electrical Engineers, one of IEEE’s predecessors.

In 1893 he invented a standard of measurement that was later named after him. The Weston cell is a wet-chemical cell that produces a stable voltage for calibrating voltmeters. It was the international standard from 1911 to 1990, when it was replaced by the Josephson junction array chip.

Weston was a founding member of the Newark College of Engineering board of trustees. The college became the New Jersey Institute of Technology. Some of his inventions, instruments, and writings are maintained at NJIT’s library and its Weston Museum.

He was awarded 334 U.S. patents before his death in 1936 at the age of 86.

MILESTONE CEREMONY

Weston’s innovations were honored on 23 September during a ceremony at NJIT. A plaque mounted in the main lobby reads:

Edward Weston and the Weston Electrical Instrument Company introduced the first portable and direct-reading current and voltage meters in 1888-1893. Weston's inventions enabling these meters included: the first truly permanent magnets; temperature-insensitive conductors; low-resistance and non-magnetic springs; metal coil frames where induced eddy currents provided pointer damping (1887); the electric shunt (1893) for the measurement of large currents; and multiple current ranges in a single meter.

This article was written with assistance from the IEEE History Center, which is partially funded by donations to the IEEE Foundation.

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