In 1817 an German inventor called Dietrich Uhlhorn used a device for measuring the spindle speed of machines. From 1840, it was capable of measuring the operational speed of locomotives. And almost 200 years later, we have the dial on all sporty motorcycles on the market.
The first all tachometers were mechanical, based on measuring the centrifugal force. The tachometer device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but as microprocessors and high-tech electronics finds its way into the motorcycle industry, digital displays are increasingly common.
Most sport motorcycle riders love tachometers, though opinions are split between dark- and light colored backgrounds. Personally, the Yamaha YZF-R1 with black background and blue illuminated LCD on both sides of the rev counter has it all. The full sweep of the white needle, which looks a bit illuminated at night by the blue light, as the ignition is switched on is neither too slow, nor too fast. And if it's a motorcycle with an analogue speedo, both needles must sweep in complete balance when you turn the throttle width open. The whole effect of the dash is even better at night when the numbers glow in the gloom. A light tinge of green or blue seems to be the absolute favorite with sport motorcycle riders. And not forget that the font of the speedo is also crucial, the serif font-type on the Yamaha YZF-R1 is perfect, as is its size and spacing. Simplicity is the key factor and numbers mustn't be too tightly spaced or too widely-spaced., and graduations every 500 rpm are just right.