[Fede]’s wife uses a pair of digital calipers to take measurements of fruits, leaves, and stems as part of her field research. Usually this means taking a measurement and writing it down in a log book. All things must be digitized, so [Fede] came up with a way to wirelessly log data off a pair of cheap Chinese calipers with a custom-made Bluetooth circuit.

Most of these cheap Chinese digital calipers already have a serial output, so [Fede] only needed to build a circuit to take the serial output and dump it in to an off-the-shelf Bluetooth module. He fabbed a custom circuit board for this, and after seeing the increased battery drain from the Bluetooth module, decided to add an external battery pack.

In addition to etching his own board for sending the serial output of the calipers to a Bluetooth module, [Fede] also put together a custom flex circuit to connect the two boards. It’s just a small bit of brass glued to a transparency sheet etched with ferric chloride, but the end result looks amazingly professional for something whipped up in a home lab.