Post by thread:PIC14000 temperature sensor problems.....

Hello everyone! I'm having a problem I thought you guys might be able to help me with. I am trying to use the PIC14000's internal temperature sensor. I am also using the CCS "C" compiler. CCS only recently implemented support for the temperature sensor so I'm not sure how tested this feature is. However, they claim that they get very good numbers from their example program. My experience has been that I get a good temperature reading the first time a reading is taken. On subsequent readings, the temperature is 6 to 8 degrees celcius too low. If I cycle power, the first is again good but later ones are not. Any ideas? I've tried covering the window on the device. I've tried different capacitors. The A/D conversion works fine with the analog input pins. I get very accurate and consistent A/D readings. -- --- Paul Greenwood --- ***************************************************************************** * spam_OUTpaulgTakeThisOuTsynopsys.com * * 512-306-6294 (w) 512-913-8595 (c) Sam Hill -- Friday night * * 512-292-0849 (h) 888-562-1813 (p) Corpus Christi bay -- Saturday * *---------------------------------------------------------------------------*

{Quote hidden}> From daver Tue Oct 21 08:50:50 1997 > To: .....paulgKILLspam@spam@epic.com > Subject: Re: PIC14000 temperature sensor problems..... > Content-Length: 2061 > X-Lines: 53 > > Dear Paul, > Thank you for your reply. I actually looked into this matter > early in the development and found that the very lowest dielectric absorption > capacitors available in surface mount are polypropylene and > polyphenylene-sulfide, each which have a dielectric absorption of 0.05% > to 0.10% at 23 degree C. Digikey offers these as their ECH-U family > of Panasonic caps at about $0.40 each in 100 quantity. > > Dave Reinagel > > P.S., do you mind if I post this to the PICLIST? > > > > From paulgKILLspamepic.com Tue Oct 21 06:58:08 1997 > > X-organization: EPIC Design Technology, Inc. > > Subject: Re: PIC14000 temperature sensor problems..... > > To: daver (Dave Reinagel) > > X-Mailer: ELM [version 2.4 PL24] > > Content-Type> : > text> > > Content-Length: 1242 > > X-Lines: 30 > > > > > > > > Dear Paul, > > > I saw your posting, but never saw any response. Today I am about > > > to start coding my PIC14000 temperature reading code, and wanted to find > > > out if you solved your problem (there's no teacher like history). > > > Thanks in advance. > > > > > > Dave Reinagel > > > Auspex System, Inc. > > > (408) 986-2099 > > > > > > > The problem was fixed by using a capacitor with a lower dialectric > > absorbtion. Check out the A/D converter docs in the Microchip tech. ref. > > There is a note that suggests 3 different capacitor types. One is a white > > teflon cap but I wa able to find one of these. I don't remember what the > > others were but everything was fixed by this. > > > > You're welcome. > > > > -- > > --- Paul Greenwood --- > > > > ***************************************************************************** > > * .....paulgKILLspam.....synopsys.com * > > * 512-306-6294 (w) 512-517-0705 (c) Sam Hill -- Friday night * > > * 512-292-0849 (h) Corpus Christi bay -- Saturday * > > *---------------------------------------------------------------------------* > > * Reality Is A Concept! * > > ***************************************************************************** > > > >From EraseMEpaulgspam_OUTTakeThisOuTepic.com Fri Oct 24 13:31:59 1997 > Yes, you can post it. -- --- Paul Greenwood ---