Water meters are used to measure the volume and/or the rate of the flow of water. A water meter may include a mechanical system, such as a propeller, a disc, a piston, or the like, that moves in relation to the water flowing through the meter. The mechanical system may drive a magnet that generates a magnetic field that changes in relation to the water flowing through the water meter. A sensor, sensitive to the magnetic field, may detect the changes in the magnetic field and generate a corresponding electrical signal. The signal may be measured locally or transmitted to a remote location to be measured. The measured signal may be translated into a metric, such as water volume, rate of flow, or the like.
Tampering may disrupt the operation of the water meter and affect the resulting metric. For example, where there is a monetary charge as a function of the volume of water consumed, there may be a motivation to tamper with operation of the water meter to make the meter report a value less than the actual amount of water consumed. Water meters that use a changing magnetic field may be susceptible to magnetic tampering.