We’re demonstrating a float level sensor with our ultrasensitive bipolar switch sensor, the ADT501.
When we power up the circuit, the sensor detects the magnet positioned 4 inches below.
You heard right, the sensor actually detects the magnet over 100 mm away to activate the pump.
When the magnet reaches level with the sensor, the sensor signals to turn the
pump off. It’s very precise, stopping well within one millimeter despite the
magnet floating inside the bottle around two inches away. Since we didn’t add hysteresis,
you can see the sensor periodically turn the pump on and off until the magnet is perfectly level.
How is the sensor able to achieve such precision?
This sensor is an ultrasensitive polarity switch usually used for rotation sensing.
But it can detect single-axis magnetic fields too, and that’s exactly how we use it in this demo.
Here is the typical sensor performance showing remarkable resolution as a polarity detector.
In our float sensor demonstration, the sensor is oriented to detect the
Y-axis field component. The graph is the simulated magnetic field of the
magnet we used in the float. The ADT501 can detect this magnet from four inches away.
As the magnet travels towards the sensor, the Y-axis field reaches a maximum and
keeps the same polarity. Only when the magnet crosses the sensor does the polarity reverse.
After the polarity reversal, the field increases rapidly, which trips the sensor.
Using the Y-axis field component and a bipolar sensor is a robust
method to prevent double switching, which can be a common problem when
trying to sense the X-axis field component. Moreover, it allows for easy calibration
because the polarity reversal is always inline with the center of the magnet.
We’re using our new DB002 evaluation board to interface our sensor to a large contactor.
The ADT501 itself is a micropower sensor designed to drive GPIO pins, but the DB002 turns it into
a rugged industrial sensor with transient protection and high load driving capability.
The sensor is below the float now, and we can actuate the relay by passing the
magnet. We set a level, and the sensor will detect when the magnet crosses its plane.
We’ll give the pump some voltage.
The sensor can detect the magnet even in this larger jar, which introduces an airgap of up
to four inches. That’s a ridiculous amount of design margin for a sensor to operate in.
Here are the boards we used for this demo.
Key features for ADT501-10E rotation sensors include:
Wide magnetic operating latitude; Ultralow power suitable for battery operation;
Small package size; And wide temperature range.
Click email or call for more information, or to buy parts and evaluation boards today.
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