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

Utility Meter applications for TMR technology
In our increasingly connected world, the concept of remote monitoring
of meters and sensors used for commercial and residential utilities,
such as water, electricity, and gas distribution, have grown from a
good idea to a strategic business opportunity for sensor and
semiconductor companies that produce the novel components
necessary for these applications.
Conventional meters are often based on decades old mechanical
technology, that is not easily upgradeable to produce the electronic
output necessary for remote monitoring applications. MTJ magnetic
sensors have numerous applications in these monitoring systems,
ranging from counting rotations of gears in a flow meter to electrical
measurements, such as current detection. The TMR sensor’s electronic
output, low power consumption, high sensitivity, and stability make it
a practical and desirable technology for use in remotely monitored
metering applications.
Water meter
Generally magnetic sensors can be used to count the rotation of a
wheel in a water meter, thereby replacing the expensive mechanical
counting mechanism for a lower cost, higher accuracy electronic
system that is compatible with remote metering requirements. In this
application, a magnet is often placed on the mechanical water meter's
rotating shaft, and a magnetic sensor is placed in an appropriate
position to sense the rotation of the shaft, in order to provide an
electronic signal representative of the rotation of the shaft. In the
simplest implementation, 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 per minute (rpm). The pulses
may be counted by digital processing electronics, yielding a number
that is representative of the amount of water that flowed through the
meter.
Compared with old fashioned electromechanical reed or inductive
Wiegand Effect sensors, the benefits of a TMR sensor are:
High frequency response
Small-size
Easy installation
Solid State
Unlimited endurance

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.