# ADXL362 reference value in the reference configuration for active motion detection

Hello,

I'm DFAE. I have a question about the reference value in the reference configuration for active motion detection of ADXL362 from my customer. I couldn't find concrete figures about that on the datasheet and this site. Could you please advise me about the reference value?

Best Regards,

Akira

## Top Replies

Parents
• Hi ,

Sorry for the late reply. What do you mean by reference value? If I understand correctly, you may be referring to the threshold that is set in ADXL362's THRESH_ACT registers:

You may find page 36-37 of the datasheet useful.

Hope this helps!

Best regards,
John

• Hi John,

I would like to know threshold level in the reference configuration of Activity Detection.

In Absolute Configuration, user can set the threshold. But in the reference configuration, it is defined internally.

Best regards,

Akira

• Hi ,

Sorry for taking too long as we have just been back from a holiday.

What the datasheet means to say that its reference value changes. I think it would be better to provide an example,

Assume that you have set the Threshold to be 0.5g, activity timer is set for 1s, the accelerometer on its normal position, (z-axis on the gravity axis and the x & y to the plane perpendicular to it):

Assuming the accelerometer has been static for a long time, its Reference will be set to 1g. Current Acceleration reading is also at 1g at this point
Which means for Equation 1:

ABS(Acceleration − Reference) > Threshold   -> ABS(1g - 1g) > 0.5g, will be false so therefore at this time, no activity is recorded.
Let's say that you subject the accelerometer to a vertical motion and the current Acceleration value is sustained at 2g for 1 second:

ABS(2g - 1g) > 0.5g, would be true.
Then, when you sustain this movement (2g for a long time), the Reference value would then become 2g.

ABS(2g -2g) > 0.5g would be false.

Hope this helps!

Best regards,
John

• Hi John,

Thank you so much for your explanation. I understand.

I have two questions about that. Is the maximum reference value same as the measurement range?

How much time does it take " for a long time"?

Thanks & regards,

Akira

• Hi ,

Yes, that would be the case. Although keep in mind that once you reach that, you must next sustain a lower acceleration for the next samples to trigger the activity detection.

I'm sorry for having misled you, here's a powerpoint presentation (with animations) that could help you understand the concept. You would want to start on Slide 4.

Best regards,
John

• Hi John,