If you or someone you know is diabetic, it’s a good idea to have a glucometer in your life. They are cheap and plentiful, but they are actually relatively high-tech – well, at least some of them are.
The gauges themselves don’t look like much, but that’s misleading. A battery, several parts, a display and enough controller to do things like memorize readings seem to cover everything. You won’t be surprised, of course, that you can get the whole affair. “on the chipBut it turns out that the real magic is in the test strip, and getting a good reading from the tape requires more metrology than you might think. An ordinary device requires accurate current measurement up to 10nA. The readings must also be adjusted for temperature. The device is surprisingly complex for something that looks like part of consumer equipment for almost disposable use.
Of course, all the time there are reports of new technologies that will not require stick with a needle. So far, none of them have been necessary for one reason or another, but that, of course, may change. The GlucoWatch G2, for example, was a watch that could read blood sugar, but – apparently – was unable to cope with sweating.
Even meters that are constantly monitored still work in more or less the same way as cheap meters. As Dan Maloney of Hackaday told in detail a few years ago, Continuous glucose monitors leave a small sensor under your skin and measure fluid in your body, not necessarily blood. But the way the sensor works is usually the same.
For the purposes of this article, I will only talk about the traditional meter: you put a test strip, prick your finger and let the test strip absorb some blood.