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Help with using the AD22151 Hall Effect Sensor

Question asked by lostinspacebar on Dec 22, 2011
Latest reply on Jan 6, 2012 by rdowning

Hi,

 

I am not sure if this is the right category for this sensor. This is the closest I have found in the available categories.

 

I am trying to use the AD22151 Hall Effect sensor. I am however having trouble understanding the gain and offset settings for the sensor.

 

The data sheet is at http://www.analog.com/static/imported-files/data_sheets/AD22151.pdf and the gain and offset settings are described on page 5/8.

 

To start, the Offset is supposed to be 1 + (R3 / R2 + R4) * (Vcc - Vout). Why does Vout factor into the offset? Shouldn't the offset be consistent over the range of output from the hall-effect sensor?

 

Even in the example calculation for R3/R2 and R4, part 4 shows ((Vcc / 2) - 1) / Vcc = 0.375, but with Vcc = 5V (which is what the example is using), that equation should equal 0.3, not 0.375.

 

Am I missing something? I am trying to make the sensor be unipolar and operate in the range ~0-350G.

 

Any help would be greatly appreciated.

 

Thanks,

Aditya

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