WEBVTT

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♪ Turn, turn, turn... ♪

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Hi, I'm Jay Brown from NVE Corporation.

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Today we're going to take a look at a product
demonstrator for NVE's

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GT Series gear-tooth sensors.

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These sensors use high-sensitivity,
low-hysteresis GMR,

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for a wide air gap tolerance.

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Different versions are available to
detect any size gear teeth.

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Analog versions provide sinusoidal outputs.

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Digital versions have a 50% 
duty cycle modulated current.

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This demonstration has:

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* The gear-tooth sensor;

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* An inexpensive Ceramic 8 bias magnet mounted

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0n the opposite side of a
circuit board from the sensor;

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* Simple amplifier electronics;

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* A micrometer mechanism to vary the air gap;

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* A motor-driven gear;

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* A meter to show the sensor current; and

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* A two-channel oscilloscope
to show the sensor outputs.

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For this for this demo,
we're connected to an external 'scope.

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There are three types of GT Sensors:
* Single-bridge analog sensors;

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* Dual-bridge analog sensors; and

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* Digital sensors.

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A biasing magnet provides field,
and the flux lines are deflected

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into the direction of sensitivity
by passing metal gear teeth.

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The sensor produces a sinusoidal output
with one cycle per tooth.

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Let's go to the demonstration.

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First, we have the ABL004 
single-bridge analog sensor.

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So I'll turn the motor ON.
As the gear spins, you see a sinusoidal output

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on the oscilloscope.

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The sensor current is shown on this meter.
Typical sensor current is just one milliamp

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for an ABL004 single-bridge sensor 
with a 5-volt supply.

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This is a typical 1.5 millimeter sensor-to-magnet
spacing...

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As I increase the air gap, you can see the
output amplitude decreases,

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but stays a symmetrical sine wave.

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The amplifier has a gain of about 20, so the
amplitude--even at the large distances--

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is several millivolts.

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With a large gear like this, 
the sensors typically

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operate over at least a 5 millimeter airgap range.

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Now we have an ABL014 dual-bridge analog sensor
and two channels on the 'scope.

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The sensor is positioned approximately 4 millimeters
away from the gear tooth.

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The dual-bridge sensor has phase-shifted outputs,
providing direction information.

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Sensor current is typically 2 milliamps; 
a maximum of 2.5 milliamps.

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Current is shown on the meter here.

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The third demonstration is an 
AKL-Series digital sensor.

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With this sensor, you see a 50% duty-cycle
digital output.

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This provides speed information.

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As I change the air gap, 
the output doesn't change.

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And if I turn the gear slowly by hand,
you see these sensors

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work to zero speed, or DC.

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This is a current-modulated 2-wire device:

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the current switches between 4 milliamps, 
and 8 milliamps

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to indicate a gear tooth.

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So to sum up,
we've shown that GT Sensors are a robust way

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to detect gear rotation, 
with a wide air-gap tolerance.

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Click, e-mail, or call us for more information.