From PICLIST@MITVMA.MIT.EDU Fri Nov 15 11:07:45 2002 Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-7.13) id A601780140; Fri, 15 Nov 2002 11:07:45 -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 <8.007DD282@cherry.ease.lsoft.com>; Fri, 15 Nov 2002 13:53:37 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8d) with spool id 7352 for PICLIST@MITVMA.MIT.EDU; Fri, 15 Nov 2002 13:53:31 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 7876; Fri, 15 Nov 2002 13:52:38 -0500 Received: from *unknown [65.112.57.227] by mitvma.mit.edu (IBM VM SMTP Level 320) via TCP with ESMTP ; Fri, 15 Nov 2002 13:52:36 EST X-Warning: mitvma.mit.edu: Host *unknown claimed to be webmail.saltonusa.com MIME-Version: 1.0 X-Mailer: Lotus Notes Release 5.0.10 March 22, 2002 X-MIMETrack: Serialize by Router on NOTES/SALTON(Release 5.0.10 |March 22, 2002) at 11/15/2002 12:53:15 PM, Serialize complete at 11/15/2002 12:53:15 PM Content-Type: text/plain; charset="us-ascii" Message-ID: Date: Fri, 15 Nov 2002 12:53:12 -0600 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: llile@SALTONUSA.COM Subject: Re: [EE]:Pressure sensor confusion To: PICLIST@MITVMA.MIT.EDU X-RCPT-TO: Status: R X-UIDL: 277600715 X-Evolution-Source: pop://mailinglist%40farcite.net@mail.farcite.net/ X-Evolution: 00000795-0000 Drifting off-topic a little... Herbert Graf wrote: >pressure reported on our local weather channel. After a few days I had enough info to put those values into Excel and have it apply it's "magic" to generate an equation for me. Turned out to be rather accurate (had to use a 1st order polynomial for best fit). A similar procedure should work in your case. TTYL Oh how often I use excel and it's magic. But there is something that EXCEL doesn't seem to do very well. Lets say you have a couple of columns of data, maybe from your pressure sensor or your thermistor or your automatic bubblegum chewer or something else. What you'd like to do is predict what the output will be when a slightly different input occurs. "No problem, just insert a blank row in your spreadsheet and interpolate" you says. Now try inserting, say, 1500 numbers "between" the data you already have. Tedious, huh? I always wanted a function that would just take a range of numbers and interpolate into them based on another input number. Sort of like "vlookup()" which I have used a lot, but instead "vinterpolate()". Anybody ever confronted this problem? Dang if this was in old Lotus 1-2-3 I would have already written a macro to do this. -- Lawrence Lile Herbert Graf Sent by: pic microcontroller discussion list 11/15/02 12:03 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [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? I'm not familiar with that sensor but generally they aren't perfectly linear and need quite an "interesting" formula in cases where full swing is necessary. What I did with my (for an atmospheric pressure project) is record the value the sensor put out every hour and recorded the atmospheric pressure reported on our local weather channel. After a few days I had enough info to put those values into Excel and have it apply it's "magic" to generate an equation for me. Turned out to be rather accurate (had to use a 1st order polynomial for best fit). A similar procedure should work in your case. TTYL -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.