>-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] >On Behalf Of Peter L. Peres >Sent: 21 October 2004 15:33 >To: Microcontroller discussion list - Public. >Subject: RE: [PIC] Traction Control / Wheelspeed sensing > > > >On Wed, 20 Oct 2004, Michael Rigby-Jones wrote: > >>> simple coil based VR sensor would be much cheaper to manufacture and >>> more robust, but I don't know of any sources for low >quantities at good >>> prices. >>> >>> imho you don't want one of those for his application. Traction >>> control must work at ~0 wheel speed. >>> >>> Peter >> >> Why would this not work at zero wheel speed? Hall effect >devices work >> fine with static magnetic fields. Also I am a little unsure >as to why >> this would be a problem anyway, zero output = zero wheel speed. Also >> surely zero wheel speed is not a common condition for traction >> control, ABS perhaps... > >A VR sensor of the kind described is passive, it consists of a >coil and a >magnet. The output voltage is nearly zero at low speed. The >active type of >VR sensor (using lm*** and mitsumi chips) does give signal at very low >speed but may be more expensive than differential gmr. The >only reason I'd >think of to use active VR instead of gmr is low temperature >behavior. But >they have that fixed now. > >Peter Peter, the quotes above are a bit out of context, the second post from me above was refering to an active sensor using a hall effect device coupled with signal conditioning circuitry. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= _______________________________________________ http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist