Magnetic Rotary Position Sensors

The ams.com website is down currently so I couldn't see the datasheet, but that's really impressive if they can achieve this accuracy, and if the resolution is high. Glad you're investigating!!! I wonder if that means people don't need to spend a fortune on optical encoders for some high-accuracy applications. For a tool application, it would be interesting to know if motors/cables nearby or any other magnetic fields affect it. Have you noticed any fluctuations in your measurements?

EDIT: just saw the Farnell link. That's very low cost! But, I was unsure, the datasheet on the Farnell site said +-0.5 degree accuracy, is this different to the manufacturer site? I guess with gearing and keeping a count of revolutions, that is still pretty good. But then there is the issue of eliminating backlash I guess :-(

I remember reading some micrometers don't use optical encoders either, but use some accurately spaced parallel PCB tracks, and capacitance. Just as a slight digression,  it doesn't help your use-case directly, but the FRDM-KL25Z boards have a lot of capacitive sensor inputs. I wonder if they can be re-tasked to some measurement purpose. That would be pretty amazing.

The ams.com website is down currently so I couldn't see the datasheet, but that's really impressive if they can achieve this accuracy, and if the resolution is high. Glad you're investigating!!! I wonder if that means people don't need to spend a fortune on optical encoders for some high-accuracy applications. For a tool application, it would be interesting to know if motors/cables nearby or any other magnetic fields affect it. Have you noticed any fluctuations in your measurements?

EDIT: just saw the Farnell link. That's very low cost! But, I was unsure, the datasheet on the Farnell site said +-0.5 degree accuracy, is this different to the manufacturer site? I guess with gearing and keeping a count of revolutions, that is still pretty good. But then there is the issue of eliminating backlash I guess :-(

I remember reading some micrometers don't use optical encoders either, but use some accurately spaced parallel PCB tracks, and capacitance. Just as a slight digression,  it doesn't help your use-case directly, but the FRDM-KL25Z boards have a lot of capacitive sensor inputs. I wonder if they can be re-tasked to some measurement purpose. That would be pretty amazing.

shabaz,

the Farnell link is for an earlier board with a lower resolution, it works the same way though. The issues with the higher rez magnetic boards is noise induced in the Hall sensors and non linearity hence the first topic.

I'm working on this in my spare time so I've only just wired up the board. Need to get the I2C communication working next.

However I will see if it is affected by motors and large chunks of steel etc.

The encoders still have their purpose; firstly they go to even higher resolution (2000 pulses per revolution no exception in robotics). Secondly, resolution is not the only concern:

• Accuracy is not 14-bit, as you have 2.7 bit rms noise. Of course you can average, but that will cost speed
• Sampling rate is 11kHz, so in very fast rotating axes the bandwith of measurement is impaired; not so with encoders

Nevertheless, magnetic rotational encoders have a very wide range of applications, and it's cool to measure just by adding a magnet!

A company that has made a very high accuracy motor driver for us told me that they're primarily using IC's from IC-Haus: http://www.ichaus.de/keyword/Magnetic%20Encoder%20iCs.

This company is also interesting: http://www.rls.si/en/am512b-9-bit-rotary-magnetic-sensor-chip--15882#ElementMediaList40407