VIEW FROM THE BENCH AUDIO LEVEL METERS

It’s 1861, and James Clerk Maxwell (whose name now describes magnetic flux) and his chums take a break from zapping frogs’ legs, influencing Einstein, and shooting lightning between big Frankenstein Balls, to sit themselves down in front of the ancestor of all audio level meters — a galvanometer.

The British Association for the Advancement of Science has deputised them to come up with the first proper set of electrical units. Among his experiments, Maxwell measures grams of magnetic force produced by different quantities-per-second of electricity flowing through his galvanometer — exactly the same forces which cause deflection of the needle in a VU meter.

Maxwell’s definitions, published in 1863, are the roots from which more or less all of today’s electrical units stem, though not without occasionally branching off. Before long, Maxwell’s unit of resistance is thought too small, so it gets multiplied by a , and re-branded as the Ohm. Likewise, electromotive force is multiplied by , and called a Volt. 20 years later the French not only stopped the British making the Volt and the Ohm 10 times bigger again, but also changed thefrom the Weber to the Ampere. Sacré bleu! So it carried on for the next 100 years, with a network of tweaks and inconsistencies that can leave amateur historians out on a limb.