From PICLIST@MITVMA.MIT.EDU Fri Nov 15 11:05:34 2002 Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-7.13) id A57EB0170; Fri, 15 Nov 2002 11:05:34 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <0.007DD3FA@cherry.ease.lsoft.com>; Fri, 15 Nov 2002 13:51:21 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8d) with spool id 7303 for PICLIST@MITVMA.MIT.EDU; Fri, 15 Nov 2002 13:51:15 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 7782; Fri, 15 Nov 2002 13:50:30 -0500 Received: from *unknown [64.69.111.211] by mitvma.mit.edu (IBM VM SMTP Level 320) via TCP with ESMTP ; Fri, 15 Nov 2002 13:50:29 EST X-Warning: mitvma.mit.edu: Host *unknown claimed to be imtrant1.imtra.com Received: from maxengineering1 ([192.168.1.9]) by imtrant1.imtra.com with Microsoft SMTPSVC(5.0.2195.4905); Fri, 15 Nov 2002 13:49:47 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2911.0) X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300 Importance: Normal X-OriginalArrivalTime: 15 Nov 2002 18:49:47.0359 (UTC) FILETIME=[C52B1EF0:01C28CD7] Message-ID: Date: Fri, 15 Nov 2002 13:49:45 -0500 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: Paul Hutchinson Subject: Re: [EE]:Pressure sensor confusion To: PICLIST@MITVMA.MIT.EDU In-Reply-To: <000e01c28cca$41a351e0$36313fd1@xero> X-RCPT-TO: Status: R X-UIDL: 277600714 X-Evolution-Source: pop://mailinglist%40farcite.net@mail.farcite.net/ X-Evolution: 00000794-0000 I checked the data sheet and this sensor is linear with an output of 0.45 V/kPa and an offset of 0.2 V to 0.425 V @ 0 kPa. So the output function is: kPa = (Vout - Voffset) / 0.45 Your measured results look good (1.845 - 0.243) / 0.45 = 3.56 kPa (1.565 - 0.243) / 0.45 = 2.94 kPa The sensor is specified as +/-5% and these values are within +/-2%. To calculate the delta between two measured points you can ignore the offset because it is constant. 1.845V - 1.565V = 0.28V 0.28V / 0.45V/kPa = 0.622kPa which is within 1.25% of your measured difference of 0.615kPa. Hope this helps, Paul > -----Original Message----- > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of John Pearson > Sent: Friday, November 15, 2002 12:13 PM > Subject: [EE]:Pressure sensor confusion > > > I am having problems figuring out how to use my Motorola pressure > sensor MPS5010dp. > > The offset voltage is .243v. no pressure applied. > I take two seperate vacuum readings: > > 1.845 v = 3.607 Kpa > 1.565 v = 2.992 Kpa > > the difference in Kpa is .615 Kpa. > > But if I take the difference in voltage output = .280 volts, and > calculate the Kpa for the voltage difference I get .1703 Kpa. > > Why is this? > > Please assume I am younger than 9 or older than 40 and just a hobbiest. > > Thanks > John > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.