♪ AC, electricity ♪
♪ DC ♪
Hello.
Today we're previewing a unique bipolar analog magnetic sensor
as a current sensor.
Most magnetic sensors are "omnipolar," meaning the output is positive
regardless of field polarity.
So used as current sensors, omnipolar sensors produce a
rectified output.
But this sensor, code-named the AAV006,
is "bipolar," so it detects field polarity
as well as magnitude.
To demonstrate, we mounted a sensor on this board,
and glued it to a current-carrying trace.
This replicates a sensor and trace on opposite sides of a circuit board.
Ampere's law can be used to calculate The magnetic field.
The PCB is 0.8 mm thick, and the sensor die are approximately
0.4 mm above the bottom of the package.
So "r" is 1.2 millimeters,
the field is 1.67 Oersted per amp,
and the sensitivity should be about 15 millivolts per amp
with a nine volt supply.
Full scale is 20 Oersteds, or about 12 amps.
The sensor is powered by a nine-volt battery.
This supply puts out plus or minus pi amps.
We corrected for sensor offset in the 'scope.
And the sensitivity is within specification tolerances
of the 15 millivolts per amp we calculated.
When we reverse the current...
...the sensor output goes negative, since the sensor is bipolar.
So to sum up, the advantages of GMR sensors
as current sensors are:
Negligible insertion resistance;
A wide current range;
Inherent electrical isolation;
and unlike inductive sensors, GMR sensors can measure
down to zero frequency as we just demonstrated.
Call click, or e-mail for more information.