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DRV5015-Q1: best magnet for the job

Part Number: DRV5015-Q1

Dear Sir/Madam,

I am desinging a test setup for a new shift drum in a geardbox. I need to be able to measure the angular position of the drum (360 degrees), this has to be done  with an off-axis set up because a lack of space for a end of shaft set up. In the datasheet of the sensor it states that it is suited for this kind of set up, there is however little info according to the magnet used for the set up. As i understand, the more poles the magnet has the beter the resolution will be. But else where on the internet there are sensors which just use diametrical magnets so it made me wonder how the magnet relates to the accuracy and resolution of the sensor. Can you please explain the matter to me.

With kind regards,

Jop Schilder 

  • Hello Jop,

    Thank you for using the TI forum. As for resolution, when using 2 Hall latch sensors (for a quadrature output), the number of rotation counts you can get is 2 times the number of poles of the magnet. So, for example with an 8-pole magnet and 2 sensors, you can get 2*8=16 counts per revolution (CPR), while with just a 2-pole magnet (diametrical magnet) you can get 2*2=4 CPR. If only using one sensor, then you only get one count per pole of the magnet.

    For some more information about encoding see this TechNote: www.ti.com/.../sboa200.pdf

    If you are looking to buy some multi-pole magnets, I know that Pololu (www.pololu.com) currently carries some small ceramic 6 & 10 pole magnets.