Sinclair Wrist Calculator
&
Quik-Check wrist calculator
Featured on this page are two wrist calculators, the Sinclair Wrist Calculator and the Quik-Check. Wrist calculators are pure calculators for strapping to the wrist and should not be confused with calculator-watches which are combined watches and calculators.
In calculator development the wrist calculator was a dead-end. It probably seemed a good idea in the mid-1970s when semiconductor manufacture had developed to the point at which a true "calculator-on-a-chip" could be produced, additionally requiring only keyboard, display, battery, and case to produce a calculator. Although everything was squeezed into a very small space, these wrist calculators are still rather large and chunky devices when strapped to the wrist.
They were soon overtaken by the rapid development and drop in prices of calculator watches, such as the Pulsar and the Compuchron models, which combined a calculator and a watch in a much smaller and more elegant casing. Also, credit-card sized calculators were just being introduced, such as the Casio Mini Card LC-78, which could be carried in a pocket while taking up negligible space.
Here are details of the only two known models of wrist calculator, the Sinclair Wrist Calculator and the Quik-Check.
Sinclair Wrist Calculator
Display is 8 digits, red LED.
4-functions, %, memory, square root.
8.1v (6x mercury cells).
Integrated circuit - Mostek MK50321N, here date coded mid-1976.
Size: 47 x 45 x 18 mm (1.9 x 1.75 x 0.7 ins).
Made in England.
1977.
Was available only as a self-assembly kit, by mail order from Science of Cambridge, previously Sinclair Instrument Ltd.
There appear to be two versions of this calculator, see photograph below.
Total price was £11 Sterling (about US$20).
Clive Sinclair was always interested in making tiny versions of common electronic items. Here, into the smallest practical volume he managed to squeeze the LED display and chip used in other Sinclair calculators (the Sinclair Cambridge Memory and Cambridge Universal), which were then becoming obsolescent.
