Smart questions
Smart answers
Smart people
Join Eng-Tips Forums

Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

slippedangel (Electrical) (OP)
25 Jul 02 6:56

I am currently using the philips 8051 to detect a magnet passing an AMR sensor. Does anyone have any ideas or recommended reading to get near 100% detection and near 0% false activation from noise.

In the perfect situation the digitized signal is a single sin-wave pulse with polarity depending on the magnet orientation. In reality this get distorted by magnet speed/offset/angle/etc

The 8051 is 22Mhz with 1kB RAM so I can't really do any complex spectral analysis.

Any suggestion would be wonderful.

cbarn24050 (Industrial)
25 Jul 02 9:34
Hi, I'm not sure what you mean by "digitised signal" in this application.If you have allready used analouge to digital conversion then all you need to do is trigger the 8051 from 1 of the higher data bits. If you are using the analouge signal directly then you can use a schmit trigger to remove the noise.
IRstuff (Aerospace)
25 Jul 02 10:10
There is no magic circuitry involved.  It's strictly a matter of signal to noise ratio (SNR).  You don't stipulate what near 100% means, but a 99% probability of detection with a 1% false alarm rate requires around 7:1 SNR.  

This can only come from a stronger signal, which means a stronger or closer magnet or a lower noise detector, which means possibly a more sensitive detector with integrated low-noise preamp located director at the detector.  

nbucska (Electrical)
25 Jul 02 12:55
You can reduce the noise by
1.) shielding 2.) filtering 3.) amplitude and duration


Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Back To Forum

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close