Flux Meter

A fluxmeter (aka magnetometer or Gaussmeter) is not an essential tool, but is very useful for verifying that a magnet "recharge" has worked. Not only with increased magnet strength, but for Bulle clocks in particular, you can tell if the magnet has the correct polarity. This project is quite simple to build, and can be made on a piece of Veroboard or similar without any problems.
There are a few magnetometers on the Net, but most are either too simple or too complex. This version is designed to have the right balance, and rather than using an external meter has a traditional analogue meter to show the magnet strength and polarity. Naturally, you can use an external meter if you prefer. This will reduce the overall cost, but personally, I prefer a self-contained unit if possible.
The heart of the flux meter is the Allegro Microsystems UGN3503UA Hall-effect sensor IC, U1. These devices are available for only a few dollars, and are more than sensitive enough for anything we may need to do with clock magnets. They do have one failing, and that's that the maximum flux density is rather limited. A very strong magnet won't cause any damage, but it will cause the Hall sensor to saturate. Once the sensor is saturated, a further increase of magnetic field strength does not cause the output to change proportionally, so a large flux change may only cause a small change of output level.
Some magnets that we might use today (such as neodymium-iron-boron) are more than strong enough to saturate the IC, but this isn't normally a problem. By spacing the sensor a suitable distance from the magnet (with a piece of plastic, wood or brass for example), the flux density is reduced sufficiently to ensure an accurate comparative reading.