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Language: en

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♪ High Temperature ♪

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Our venerable GMR sensors 
have high sensitivity 

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and excellent temperature stability. 

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Some of them are even more stable 

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driven with constant current
rather than constant voltage. 

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It's easy to do, and we're heading 
into the lab to test it out. 

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We'll start with an evaluation board for our
high-sensitivity AAH002 analog magnetic sensor. 

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We wrapped the sensor with 
two turns of magnet wire 

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to create a precision magnetic field. 

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We didn't want to use a permanent magnet 
for this kind of test 

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since the magnet's field 
would vary with temperature. 

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The bench supply powers the coil.

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The source meter powers the sensor 
with a constant five volts. 

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We set the amp-turns to bias the sensor
in the middle of its linear range.

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This multimeter shows the sensor output. 

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This meter shows the sensor temperature.

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We record the first data point 
at room temperature.

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Then heat the sensor to 125°C...

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...and check the output as
the temperature drops.

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100°C...

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75°C...

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50°C...

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Now let's try it 
with a constant current source.

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There are several ways to make 
a current source.

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The simplest is probably to use 
one of our voltage regulators. 

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These regulators are rated to 175 C,

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which complements
the high-temperature sensors. 

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We set the current for 2.5 milliamps
to provide approximately five volts

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to the two kiloohm bridge sensor.

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25 Celsius...

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125 Celsius...

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...and some points in between.

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Here's a plot with both constant
voltage and constant current. 

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So the lab results are in.

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Constant current reduces 
the temperature coefficient by 30%.

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In addition to temperature stability, 
key specifications of these sensors include:

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high sensitivity, 

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and an extended temperature range.

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These are the parts we used for this demo.
All of them are available through our webstore.

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Click for more information, 

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or to order sensors, regulators, 
or evaluation boards.

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