X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from x2.itlnet.net ([64.19.112.8] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTPS id 2227495 for flyrotary@lancaironline.net; Thu, 02 Aug 2007 13:55:14 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.19.112.8; envelope-from=jwvoto@itlnet.net Received: from x2.itlnet.net (x2.itlnet.net [127.0.0.1]) by x2.itlnet.net (8.13.1/8.13.1) with SMTP id l72HsNpi024990 for ; Thu, 2 Aug 2007 12:54:23 -0500 Received: from itlnet.net (email1.itlnet.net [192.168.10.156]) by x2.itlnet.net (x2.itlnet.net [127.0.0.1]) id j71CsN2131915545gD ret-id none; Thu, 02 Aug 2007 12:54:23 -0500 Received: from JWVOTO (unverified [64.19.116.55]) by itlnet.net (SurgeMail 3.8l) with ESMTP id 1102-1769559 for ; Thu, 02 Aug 2007 12:54:23 -0500 Message-ID: <003701c7d52e$bda57e60$37741340@JWVOTO> From: "Wendell Voto" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: EM2 & builder issues Date: Thu, 2 Aug 2007 12:57:50 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0034_01C7D504.BBA22660" 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-Authenticated-User: jwvoto@itlnet.net 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=-2.599, required 4, autolearn=not spam, BAYES_00 -2.60, HTML_MESSAGE 0.00, SPF_HELO_PASS -0.00) This is a multi-part message in MIME format. ------=_NextPart_000_0034_01C7D504.BBA22660 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Tracy, Maybe you shouldn't had said 50th but we won't tell. Could the EM2 use LM34 temp sensors? They give 10mv/deg. F and have = very good accuracy (spec is 1 degree but I get less than .1 degree = repeatability one sensor to another)and track well, very linear. They = are what I am using, just JB welded into a hollowed out old sensor and = plan on using for oil and water temps. Wendell Fine points on the EM2: The default sensors on the EM2 are very low cost automotive types but = they are not inherently super accurate. Usually there in no big = down-side for the water or oil temp to be off a few degrees so most = builders need not go any further. If the water temp turns out to be = actually 178 instead of 180, no big deal. Super accuracy can be had = with these sensors if you go to the trouble of calibrating the = instrument but then you must get into the nitty gritty of the = calibration procedures and the troubles can begin.=20 But here is where it does matter. If you are calculating thermal = loads and heat dissipation based on differential temps (let's say water = temps in and out of the radiator for instance) a few degrees of error = can make your results meaningless. In this example, it is not uncommon = for the Delta T to be in the range of 10 degrees at some power settings. = If the error in temperature is a couple of degrees, the error is huge, = especially if the errors are in opposite directions.=20 Bottom line is, if you need very accurate readings, learn to calibrate = the EM2 if that is what you are using. To do this, you need a good = reference. The easiest way is to use a non-contact (infra-red) = thermometer. Harbor Freight and others are now selling inexpensive ones = for about $10.00. No reason for any airplane builder not to have one. = Be sure to paint the test points on the part to be measured with a spot = of flat black paint to eliminate emissivity errors. =20 Tracy (should I have said 50th? ) =20 ------=_NextPart_000_0034_01C7D504.BBA22660 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Tracy,
Maybe you shouldn't had said 50th but we won't tell.
Could the EM2 use LM34 temp sensors?  They give 10mv/deg. F = and have=20 very good accuracy (spec is 1 degree but I get less than .1 degree = repeatability=20 one sensor to another)and track well, very linear.  They are what I = am=20 using, just JB welded into a hollowed out old sensor and plan on using = for oil=20 and water temps.
Wendell
Fine points on the EM2:
 
 
 
The default sensors on the EM2 are very low cost automotive types = but=20 they are not inherently super accurate.  Usually there in no = big=20 down-side for the water or oil temp to be off a few degrees so = most=20 builders need not go any further.  If the water temp turns out to = be=20 actually 178 instead of  180, no big deal.  Super accuracy = can be=20 had with these sensors if you go to the trouble of calibrating the = instrument=20 but then you must get into the nitty gritty of the calibration = procedures and=20 the troubles can begin.
 
But here is where it does matter.  If you are calculating = thermal=20 loads and heat dissipation based on differential temps (let's say = water temps=20 in and out of the radiator for instance)  a few degrees of error = can make=20 your results meaningless.  In this example, it is not uncommon = for the=20 Delta T to be in the range of 10 degrees at some power settings.  = If the=20 error in temperature is a couple of degrees, the error is huge, = especially if=20 the errors are in opposite directions.
 
Bottom line is, if you need very accurate readings, learn to = calibrate the EM2 if that is what you are using.  To do this, you = need a=20 good reference.  The easiest way is to use a non-contact = (infra-red)=20 thermometer.  Harbor Freight and others are now selling = inexpensive ones=20 for about $10.00.  No reason for any airplane builder not to have = one.   Be sure to paint the test points on the part to = be=20 measured with a spot of flat black paint to eliminate emissivity = errors. =20
 
Tracy  (should I have said 50th?  )
 
 
------=_NextPart_000_0034_01C7D504.BBA22660--