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Author Topic: Hall effect sensor: the right solution to track very small distance variations ?  (Read 1069 times)
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Hello,

I am thinking to use one (and maybe several) ratiometric Hall effect sensor(s) to measure very small distance variations (< 5 mm) between two plates.

Is it the right choice ? Or should I use a capacitive sensor instead ?

How much is an Hall effect sensor immune to EMI /RFI if there's electronic gear at a short but bigger distance, such as ten centimeters ?

Also, where can I find suitable small magnets in Europe ?

In the  case I would measure the distance at several points with multiple sensors, are the distance curves consistent or should I expect serious differences among sensors ?

Thank you in advance.
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Linear hall sensors , like the HAL 1820 from Micronas, could be used. External magnetic field will however change the measurement results if large enough. Maybe also a hall encoder like the iC-MA from iC-Haus in the analog mode (http://www.ichaus.biz/upload/pdf/MA_datasheet_B3en.pdf ).

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Can you say more about the application? For example, how large are the plates, how far apart are they (minimum and maximum values), and what is in between the plates?
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At the moment this is just an idea for a possible alternative design for a force plate. My current design uses four load cells but I was thinking about a way to reduce the number of sensors.

The plate would have a size of 15x15cm and would be supported by a springs in each corner. The principle would consist in the combination of a sensor (Hall effect ?) put in the center of the plate to track the distance variations between the plate and the table according to the pressure applied on the plate and a two-axis accelerometer put closer to an edge to track the inclination according to the xy position where most pressure is applied. So the actual distance matters less than the distance variations, which would depend on spring's elasticity.

Thanks for the references. In between I have also found a supplier with a large choice of magnets: http://www.supermagnete.de/eng/
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I think hall effect analog output sensor(s) might work, but if you use more then one I suspect you might have a 'calibration challenge' to make sure they track well with each other.

Lefty
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If the plates are non-magnetic, then I agree than an analog Hall sensor and a strong magnet would be a good place to start.
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