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We’re demonstrating a float level sensor with our 
ultrasensitive bipolar switch sensor, the ADT501.

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When we power up the circuit, the sensor 
detects the magnet positioned 4 inches below.

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You heard right, the sensor actually detects the 
magnet over 100 mm away to activate the pump.

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When the magnet reaches level with the 
sensor, the sensor signals to turn the

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pump off. It’s very precise, stopping 
well within one millimeter despite the

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magnet floating inside the bottle around two
inches away. Since we didn’t add hysteresis,

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you can see the sensor periodically turn the pump 
on and off until the magnet is perfectly level.

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How is the sensor able to achieve such precision?

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This sensor is an ultrasensitive polarity 
switch usually used for rotation sensing.

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But it can detect single-axis magnetic fields too, 
and that’s exactly how we use it in this demo.

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Here is the typical sensor performance showing 
remarkable resolution as a polarity detector.

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In our float sensor demonstration, 
the sensor is oriented to detect the

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Y-axis field component. The graph is 
the simulated magnetic field of the

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magnet we used in the float. The ADT501 can 
detect this magnet from four inches away.

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As the magnet travels towards the sensor, 
the Y-axis field reaches a maximum and

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keeps the same polarity. Only when the magnet 
crosses the sensor does the polarity reverse.

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After the polarity reversal, the field 
increases rapidly, which trips the sensor.

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Using the Y-axis field component 
and a bipolar sensor is a robust

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method to prevent double switching, 
which can be a common problem when

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trying to sense the X-axis field component. 
Moreover, it allows for easy calibration

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because the polarity reversal is always 
inline with the center of the magnet.

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We’re using our new DB002 evaluation board 
to interface our sensor to a large contactor.

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The ADT501 itself is a micropower sensor designed 
to drive GPIO pins, but the DB002 turns it into

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a rugged industrial sensor with transient 
protection and high load driving capability.

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The sensor is below the float now, and 
we can actuate the relay by passing the

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magnet. We set a level, and the sensor will 
detect when the magnet crosses its plane.

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We’ll give the pump some voltage.

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The sensor can detect the magnet even in this 
larger jar, which introduces an airgap of up

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to four inches. That’s a ridiculous amount 
of design margin for a sensor to operate in.

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Here are the boards we used for this demo.

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Key features for ADT501-10E 
rotation sensors include:

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Wide magnetic operating latitude;
Ultralow power suitable for battery operation;

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Small package size;
And wide temperature range.

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Click email or call for more information, 
or to buy parts and evaluation boards today.

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Like the video if you enjoyed it,

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and subscribe to the NVE Corporation YouTube 
channel for more product demonstrations.