X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop-Diagnostic: (direct reply)\eX-PolluStop-Score: 0.00\eX-PolluStop: Scanned with Niversoft PolluStop 2.1 RC1, http://www.niversoft.com/pollustop Return-Path: Received: from relay02.roc.ny.frontiernet.net ([66.133.182.165] verified) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTP id 860543 for flyrotary@lancaironline.net; Thu, 07 Apr 2005 13:14:07 -0400 Received-SPF: pass receiver=logan.com; client-ip=66.133.182.165; envelope-from=canarder@frontiernet.net Received: from filter09.roc.ny.frontiernet.net (filter09.roc.ny.frontiernet.net [66.133.183.76]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id B203C370391 for ; Thu, 7 Apr 2005 17:13:20 +0000 (UTC) Received: from relay02.roc.ny.frontiernet.net ([66.133.182.165]) by filter09.roc.ny.frontiernet.net (filter09.roc.ny.frontiernet.net [66.133.183.76]) (amavisd-new, port 10024) with LMTP id 25225-02-84 for ; Thu, 7 Apr 2005 17:13:20 +0000 (UTC) Received: from [127.0.0.1] (67-137-87-40.dsl2.cok.tn.frontiernet.net [67.137.87.40]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id 3F5DC37038C for ; Thu, 7 Apr 2005 17:13:19 +0000 (UTC) Message-ID: <42556AA6.9030000@frontiernet.net> Date: Thu, 07 Apr 2005 12:15:18 -0500 From: Jim Sower User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040514 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Timing References: In-Reply-To: Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit X-Antivirus: avast! (VPS 0514-1, 04/07/2005), Outbound message X-Antivirus-Status: Clean X-Virus-Scanned: by amavisd-new-20040701 (2.0) at filter09.roc.ny.frontiernet.net Could a little piece of a magnetic rod embedded in either steel or Al disc (flywheel, pulley, etc.) do the trick? I always thought magnetic pickups actually involved a magnet, or at least a dominant spike of metal passing the pickup.
Magnetic reluctance sensors need a steel "tooth" on the moving disk to operate. The tooth (or teeth) must be a material that you can pick up with a magnet. Thus, aluminum won't do. You could put a steel "ring gear" on an aluminum pulley, I suppose.

The sensor has a magnet inside. When the tooth comes near, it makes an easier path for the magnetic field from the sensor magnet. (Kind of like putting the keeper on a horseshoe magnet.) This increases the magnetic field in the sensor pick-up coil, generating an electric current. This voltage "pip" is sensed by the electronics.
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