Utility Meter applications for TMR technology In our ... - ThomasNet

Power meter
A current flowing through a wire produces a magnetic field that flows
circumferentially around the wire. This magnetic field has an intensity
and polarity proportional to current magnitude and direction. Thus a
TMR sensor placed in proximity of a wire provides a voltage that can
be used to measure the current flowing through a wire. Hall Effect
sensors (“Hall sensors”) are often used for this application, but Hall
sensors are not ideal. The intrinsic thermal stability of Hall sensors is
poor because of the Hall Effect depends on carrier concentration in a
semiconducting element, which is intrinsically dependent on
temperature, thereby requiring some method to compensate.
Additionally, Hall sensors have relatively low sensitivity to magnetic
field, and they often require the presence of a permeable flux
concentrator or slotted ferrite ring to amplify the field produced by the
current flowing through the wire. This increases system size and cost
beyond the mere cost of the Hall sensor. Because of this low
sensitivity performance and inherent temperature dependence that
increases the size and cost of Hall sensor equipped meters, TMR
current sensors are much better suited for smart power meter
applications than Hall sensors.
Gas meter
Like a water meter, a gas meter is effectively a type of flow meter that
measures consumption in terms of the cumulative rotation of a
spinning shaft. In an analogous manner to their use in water meters,
TMR sensors may also be used in utility gas meter applications. In a
simple but effective implementation, a magnet is often placed on the
meter's main shaft, and a magnetic sensor is placed in an appropriate
position to sense the rotation of the magnet. The sensor output
toggles high and low when the magnet moves past the sensor, and
this produces pulses that can be converted to a measure of revolutions
of the shaft. The pulses may be counted by digital processing
electronics, yielding a number that is representative of the cumulative
amount of gas that flowed through the meter, thus yielding a measure
of gas consumption. The advantages of TMR sensor over reed
switches, Wiegand Sensors, and Hall sensors result in lower meter
cost, smaller size, and better metering reliability.