Most hackers and makers end up with a cheap pair of calipers in the toolbox at some point or another. [DiodeGoneWild] decided to take a particularly cheap plastic pair and tear them down to see what makes them tick measure.The electronics is, unsurprisingly, all contained inside the carriage which slides along the ruler. The ruler itself has an etched copper strip inside, underneath the scale sticker, with repetitive T-shaped sections. Meanwhile, the PCB in the carriage has a series of plates for capactive sensing. As the carriage slides along the copper strip inside the ruler, the capacitive sensing plates pick up varying capacitances which are directly proportional to how far the carriage has moved, allowing for precise measurement of relative position. Zeroing is a job for the user, via the ZERO button. We get to see how this works on the bare hardware level, and [DiodeGoneWild] even breaks out the oscilloscope to help show us what’s going on.[DiodeGoneWild] also notes that these calipers are particularly frustrating for how quickly they discharge batteries while in storage. This may be down to the convenience feature, wherein moving the caliper switches the display on. There’s no hard off switch here—so the caliper is always drawing some juice even when it’s just in the cupboard. This is why these things are forever turning up dead when you need them.If you’ve never pulled apart one of these cheap tools, this is a great way to see what’s actually going on under the hood. We’ve seen some other great teardowns lately, like this deep dive into a cheap pair of smartglasses. Video after the break.