X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from x.itlnet.net ([64.19.112.9] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTPS id 2157022 for flyrotary@lancaironline.net; Wed, 04 Jul 2007 01:11:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.19.112.9; envelope-from=jwvoto@itlnet.net Received: from smtpav.service (email1.itlnet.net [192.168.10.156]) by x.itlnet.net (8.13.1/8.13.1) with SMTP id l645Aiqd007543 for ; Wed, 4 Jul 2007 00:10:44 -0500 Received: from JWVOTO (unverified [64.19.115.114]) by mail.itlnet.net (Rockliffe SMTPRA 7.0.6) with ESMTP id for ; Wed, 4 Jul 2007 00:10:22 -0500 Message-ID: <000d01c7bdfa$1deb9300$72731340@JWVOTO> From: "Wendell Voto" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] MAP pressure sensors Date: Tue, 3 Jul 2007 23:27:52 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0035_01C7BDC9.C68C2D20" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 X-ITLnet-MailScanner-Information: Please contact the ISP for more information X-ITLnet-MailScanner: Found to be clean X-ITLnet-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, score=-2.463, required 4, autolearn=not spam, BAYES_00 -2.60, FORGED_RCVD_HELO 0.14, HTML_MESSAGE 0.00) This is a multi-part message in MIME format. ------=_NextPart_000_0035_01C7BDC9.C68C2D20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable After you solve the pressure sensor problem, you might try putting a = good quality capacitor or pair of capacitors (like 10ufd and .01ufd) = across the Schottky diodes to pass the ac noise back to the battery. Wendell The same approx. output indicates to me that the pressure = transducers appear to be doing identical functions with changing = altitude/ambient pressure. So I would normally say the problem has to = be down stream of the pressure transducer output, but I'm sure Tracy has = chased that rabbit. It is a puzzle=20 Al, How did you go about measuring the output at different altitudes? Did = you actually have wires running to some sort of ohmmeter while in = flight? Or did you use a pressure chamber? If pressure (vacuum) = chamber did you have a separate vacuum source on the manifold lines? = Otherwise, you would not have simulated altitude accurately.=20 David; What I said: ". . . even though the measured output from the A and B sensors are = the same when the unit is powered up (out of the plane) at different = altitudes (measured at 1400' and 5300')." was not very clear. The output measured at Ramona (1400') was = consistent; and that measured at Boulder, CO (5300') was also - within = less than a milivolt. So this would suggest that the output response is = the same, or IOW, at WOT, at different altitudes, A and B should be the = same. The sensor on A also appeared to be in fine shape in all respects. = It is true that this is not the same as pulling a vacuum on the ports = to say, 20" Hg with both at the same altitude. That test seemed more = difficult than buying a new sensor. I should know next week whether = that solves the problem. In replacing the sensor, and further studying the circuit, my son says = " I installed the new MAP sensor, and added a ground lead from the = sensor to the processor (I think the lack of a good ground return=20 was the source of the RF and other problems). He has remarked before = that his opinion is that the ground circuits on the board are not = particularly resistant to RF issues. With the diodes possibly causing interference, did you run a trial = jumper across the diodes and did that in fact fix the problem? = Otherwise you could be barking up a long and tangled tree... The thought that the power isolation diodes COULD be a source of the = problem did not come to light until we were well down the road to a = solution, and the additional filtering was added. So that test was = never done. It is speculation based on that feature being unique to my = installation, and that I seemed to be the only one with the data = settings corruption problem. Al ------=_NextPart_000_0035_01C7BDC9.C68C2D20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
After you solve the pressure sensor problem, you might try putting = a good=20 quality capacitor or pair of capacitors (like 10ufd and .01ufd) across = the=20 Schottky diodes to pass the ac noise back to the battery.
Wendell
 

 

 The same approx. = output=20 indicates to me that the pressure transducers appear to be doing = identical=20 functions with changing altitude/ambient pressure.  So I would = normally=20 say the problem has to be down stream of the pressure transducer = output, but=20 I'm sure Tracy has chased that rabbit.  It is a = puzzle=20

 

Al,

 

How did you go about = measuring the output=20 at different altitudes?  Did you actually have wires running to = some sort=20 of ohmmeter while in flight?  Or did you use a pressure=20 chamber?  If pressure (vacuum) chamber did you have a = separate=20 vacuum source on the manifold lines? Otherwise, you would not have = simulated=20 altitude accurately.

David;

What I=20 said:

“. = . . even though=20 the measured output from the A and B sensors are the = same when = the unit is=20 powered up (out of the plane) at different altitudes (measured at = 1400’ and=20 5300’).”

was not = very=20 clear.  The output measured at Ramona (1400’) was = consistent; and that=20 measured at Boulder,=20 CO = (5300’) was also –=20 within less than a milivolt.  So this would suggest that the = output=20 response is the same, or = IOW, at WOT,=20 at different altitudes, A and B should be the same. The = sensor on A=20 also appeared to be in fine shape in all respects.  It is true = that this=20 is not the same as = pulling a=20 vacuum on the ports to say, 20” Hg with both at the = same = altitude. =20 That test seemed more difficult than buying a new sensor.  I = should know=20 next week whether that solves the problem.

 

In = replacing the=20 sensor, and further studying the circuit, my son says “ = I=20 installed the new MAP = sensor, and=20 added a ground lead from the sensor to the processor (I think the lack = of a=20 good ground return

was the source of the = RF and=20 other problems).  = He has=20 remarked before that his opinion is that the ground circuits on the = board are=20 not particularly resistant to RF issues.

 

With the diodes possibly = causing=20 interference, did you run a trial jumper across the diodes and did = that in=20 fact fix the problem?  Otherwise you could be barking up a long = and=20 tangled tree...

 

The = thought that=20 the power isolation diodes COULD be a source of the problem did not = come to=20 light until we were well down the road to a solution, and the = additional=20 filtering was added.  So that test was never done. It is = speculation=20 based on that feature being unique to my installation, and that I = seemed to be=20 the only one with the data settings corruption = problem.

 

Al

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