To conduct measurements, we use unique magnetic material – Bistable
Microwire – for sensing the magnetic field and temperature/mechanical
stress in a single measurement.
Temperature sensing and stress sensing are not affected by magnetic noise
(even though the sensor is magnetic). Measurement is very different from the
one used in conventional magnetic sensor. Conventional sensor requires high
permeability (for high sensitivity) and high saturation field (for high range).
RVmagnetics sensor has permeability ~ 1 (like vacuum) and saturation field cca.
We are able to measure pressure – pressure dependence of the switching
field is perfectly linear within whole measured range – while the measurement
is completely temperature independent. It also works vice versa – we are
able to measure temperature – while temperature dependence of the switching
field is perfectly linear within whole measured range – measurement is
completely pressure independent. For the sensing – for the easy
demonstration – let’s use mobile phone sound card as an example. We need
earphone output for producing the magnetic field (serves as the excitation coil)
and microphone input to sense the signal (serves as the sensing coil).
There is no connection between the microwire and coils – Microwire can be
place inside various materials and coil system detects a signal from the
distance up to 10cm.
We transform the measured parameter (magnetic field, temperature, stress, or
others) into the time (the output is not a voltage – it is the velocity of
domain wall propagation). Hence it is better to used counter in ARM chip (here,
the output is directly number/magnetic field) or FPGA or similar fast
electronics instead of microphone (which has small sampling frequency ~7kHz).
The higher is the time resolution, the higher is the accuracy of sensor.