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ADXL1001/1002 motion indication.

Dear Miss, Mister.

I'm confused about the axix of sensitivity of your ADXL1001/1002 product.

When moving the accelerometer in the "+" direction, should i have a positive signal at the output of it (pin 30)?

When i' m pointing the accelerometer with the "+" sign to the ground (1g) i'm measuring 2.12 V

At 0g, i have 2.09V

With "+" pointing to the sky, i have 2.06V.

But, when i move the accelerometer in the direction of the "+", i'm measuring a negative pulse on the scope.

Moving in the "-" direction gives a positive one.

I,m very confused with this because we also use ST accelerometers (LIS344 for example) and their indications matches with the accelerometer motion (moving to the "+" gives a positive pulse.

Maybe i'm misinterpretating the datasheet?

Looking forward for your answer.

Best regards.

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  • Hi,

    A quick question, when you say negative pulse, is it negative voltage or is it a decreased in voltage but still positive voltage?

    Normally corresponding output increases when accelerated along the sensitivity axis. 

    Regards,

    Mark

  • Hello Mark,

    It's decreasing but positive.

    The ADXL is supplied with 4.096V and so I have a DC output round 2.05V.

    Thus, when I move to the accelerometer in the "+" direction, I should have more then 2.05V but in my case, it's less.

    I do hope I'm clear enough.

    Best regards.

    Yves.

  • Hello Yves, 

    The sensitivity directions as marked on the datasheet are correct and verified. The best way to test them is in the gravity field.  If the + side is facing down (toward gravity vector) the sensor output voltage will increase. Upward/downward movements have an accelerating portion and decelerating portion.  Based on your description, it seems you are measuring deceleration with the sensor.  We cannot comment on how other 3rd party sensors behave. 

    Hope it helps. 

  • Hello Mahdi,

    Strangely on the ADXL377, when i point  the arrow direction to the floor, it gives me a negative output.

    To be clear, supplied by 3.3V, the midpoint is at 1.649V (0g), 1.655 at 1g and 1.642 at -1g (arrow to the floor).It's the contrary of the ADXL1001/1002.

    I'm still a bit confused with this all.

    Best regards.

  • On ADXL377 the corresponding output increases when accelerated along the sensitivity axis. But it's defined oppositely for the ADXL100x family. Sorry for the confusion.

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