adding pt100 description
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pt100/mybib.bib
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404
pt100/mybib.bib
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% $Id: mybib.bib,v 1.5 2008/12/18 17:05:23 robin Exp $
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%
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%
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@TechReport{db,
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author = {R Clark, D Legge},
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title = {ETC6000 Daughterboard Design notes},
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institution = {ETC HR221850},
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year = {2004},
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key = {},
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OPTtype = {},
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OPTnumber = {},
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OPTaddress = {},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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issn = {HR221850},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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||||
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@TechReport{mil1991,
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author = {U.S. Department of Defence},
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title = {Reliability Prediction of Electronic Equipment},
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institution = {DOD},
|
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year = {1991},
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key = {MIL-HDBK-217F},
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OPTtype = {},
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OPTnumber = {},
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OPTaddress = {},
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||||
OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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@Manual{tlp181,
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title = {TLP 181 Datasheet},
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key = {TOSHIBA Photocoupler GaAs Ired & Photo−Transistor},
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author = {Toshiba inc.},
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OPTorganization = {},
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%address = {http://www.toshiba.com/taec/components2/Datasheet\_Sync//206/4191.pdf},
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OPTedition = {},
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OPTmonth = {},
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year = {2009},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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@Manual{pic18f2523,
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title = {PIC18F2523 Datasheet},
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OPTkey = {},
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author = {Microchip inc},
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OPTorganization = {},
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||||
address = {http://ww1.microchip.com/downloads/en/DeviceDoc/39755c.pdf},
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OPTedition = {},
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OPTmonth = {},
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year = {2009},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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||||
}
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@Book{wt,
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title = {Water Treatment Essentials for Boiler Plant Operation},
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publisher = {Mc Graw Hill ISBN 0-07-048291-5},
|
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year = {1997},
|
||||
author = {Robert G Nunn},
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ALTALTeditor = {},
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||||
OPTkey = {},
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||||
OPTvolume = {},
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OPTnumber = {},
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||||
OPTseries = {},
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OPTaddress = {},
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OPTedition = {},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {ISBN 0-07-048291-5},
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OPTlocalfile = {},
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OPTabstracts = {},
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||||
}
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@TechReport{pcbAI222562,
|
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author = {C Talmay},
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||||
title = {Circuit Schematic TDS Daughterboard AI222562},
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institution = {ETC},
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year = {2010},
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OPTkey = {},
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||||
OPTtype = {},
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OPTnumber = {AI222562},
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OPTaddress = {},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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@TechReport{spiraxsarco,
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author = {Spirax Sarco},
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title = {http://www.spiraxsarco.com/resources/steam-engineering-tutorials.asp},
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institution = {Spirax Sarco},
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year = {2010},
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OPTkey = {},
|
||||
OPTtype = {},
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OPTnumber = {},
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OPTaddress = {},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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@Book{aoe,
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title = {The Art of Electronics},
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publisher = {Cambridge},
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year = {1989},
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author = {Paul Horowitz, Winfield Hill},
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%author = {},
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OPTkey = {},
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OPTvolume = {},
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OPTnumber = {},
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OPTseries = {},
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OPTaddress = {},
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OPTedition = {2nd},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {ISBN 0-521-37095-7},
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OPTlocalfile = {},
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OPTabstracts = {},
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}
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@TechReport{eurothermtables,
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author = {},
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title = {Thermocouple Emf TABLES and PLATINUM 100 RESISTANCE THERMOMETER TABLES},
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institution = {Eurotherm},
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year = {1973},
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OPTkey = {},
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OPTtype = {},
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OPTnumber = {},
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OPTaddress = {},
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OPTmonth = {June},
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OPTnote = {Bulletin TT-1},
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OPTannote = {},
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OPTurl = {},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {},
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}
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@MISC{iso639-1,
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title = "ISO 639-1: Code for the Representation of Names of Languages",
|
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author = "International Standardization Organization",
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howpublished = "http://www.loc.gov/standards/iso639-2/criteria1.html"
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year = "1998"
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}
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@MISC{nano-x,
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title = "The nano-X windowing system",
|
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author = "Greg Haerr",
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howpublished = "http://www.microwindows.org/"
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year = "2003"
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}
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@MISC{X11,
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title = "The XFree86 Project, Inc",
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author = "Open Source",
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howpublished = "http://www.xfree86.org/"
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year = "1992"
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}
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http://www.xfree86.org/
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@MISC{iso639-2,
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title = "ISO 639-2: Code for the Representation of Names of Languages",
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author = "International Standardization Organization",
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howpublished = "http://www.loc.gov/standards/iso639-2/criteria1.html"
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year = "1998"
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}
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@misc{ touchscreenprod,
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author = "M. Thirsk",
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title = "Touchscreen Production Procedure : HR~222165",
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howpublished = "Internal ETC Document",
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year = "2008" };
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@misc{ touchscreensoftware,
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author = "ETC Software Dept.",
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title = "Touchscreen Software released to Production : HR~222162",
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howpublished = "Internal ETC Software (medium: 2 MMC cards)",
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year = "2008" };
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@misc{ touchscreengui,
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author = "D.J. Legge, R.P.Clark",
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title = "Touchscreen GUI Design Document : HR~222163",
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howpublished = "Internal ETC Document",
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year = "2008" };
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@misc{ gumstix,
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author = "Gumstix Inc",
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title = "Gumstix Home Page",
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howpublished = "WEB http://www.gumstix.com/",
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year = "2008" };
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@misc{ fltk,
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author = "FLTK open Source Developers",
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title = "Fast Light Toolkit",
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howpublished = "WEB http://www.fltk.org/",
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year = "2008" };
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@Book{ldd,
|
||||
author = {Jonathon Corbet},
|
||||
ALTeditor = {Alessandro Rubini},
|
||||
ALTeditor = {Greg Kroah-Hartman},
|
||||
title = {Linux Device Drivers},
|
||||
publisher = {O'Reilly ISBN 0-596-00590-3},
|
||||
year = {1998},
|
||||
OPTkey = {ISBN 0-596-00590-3},
|
||||
OPTvolume = {},
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||||
OPTnumber = {},
|
||||
OPTseries = {linux},
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||||
OPTaddress = {},
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OPTedition = {3rd},
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OPTmonth = {},
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OPTnote = {},
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OPTannote = {},
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OPTurl = {www.oreilly.com},
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OPTdoi = {},
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OPTissn = {},
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OPTlocalfile = {},
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OPTabstract = {}
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};
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@Book{bash,
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author = {Carl Albing},
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title = {Bash Cookbook},
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||||
publisher = {O'Reilly ISBN 0-596-52678-4},
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year = {2007},
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||||
OPTkey = {ISBN 0-596-52678-4},
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||||
OPTvolume = {},
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||||
OPTnumber = {},
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||||
OPTseries = {unix/linux},
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||||
OPTaddress = {},
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||||
OPTedition = {},
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||||
OPTmonth = {},
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||||
OPTnote = {},
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||||
OPTannote = {},
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||||
OPTurl = {www.oreilly.com},
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||||
OPTdoi = {},
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||||
OPTissn = {},
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||||
OPTlocalfile = {},
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||||
OPTabstract = {}
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||||
};
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||||
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||||
@Book{sedawk,
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||||
author = {Dale Dougherty, Arnold Robbins},
|
||||
title = {Sed and Awk},
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||||
publisher = {O'Reilly ISBN 1-56592-225-5},
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||||
year = {1997},
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||||
OPTkey = {ISBN 1-56592-225-5},
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||||
OPTvolume = {},
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||||
OPTnumber = {},
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||||
OPTseries = {unix/linux},
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||||
OPTaddress = {},
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||||
OPTedition = {},
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||||
OPTmonth = {},
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||||
OPTnote = {},
|
||||
OPTannote = {},
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||||
OPTurl = {www.oreilly.com},
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||||
OPTdoi = {},
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||||
OPTissn = {},
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||||
OPTlocalfile = {},
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||||
OPTabstract = {}
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||||
};
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||||
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@Book{bels,
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||||
author = {Karim Yaghmour},
|
||||
title = {Building Embedded LINUX systems},
|
||||
publisher = {O'Reilly ISBN ISBN 0-596-00222-X},
|
||||
year = {2003},
|
||||
OPTkey = {ISBN 0-596-00222-X},
|
||||
OPTvolume = {},
|
||||
OPTnumber = {},
|
||||
OPTseries = {linux},
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||||
OPTaddress = {},
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||||
OPTedition = {3rd},
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||||
OPTmonth = {},
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||||
OPTnote = {},
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||||
OPTannote = {},
|
||||
OPTurl = {www.oreilly.com},
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||||
OPTdoi = {},
|
||||
OPTissn = {},
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||||
OPTlocalfile = {},
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||||
OPTabstract = {}
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||||
};
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||||
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@Book{can,
|
||||
author = {Olaf Pfeiffer},
|
||||
ALTeditor = {Andrew Ayre},
|
||||
ALTeditor = {Christian Keydel},
|
||||
title = {Embedded networking with CAN and CANopen},
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||||
publisher = {RTC ISBN 0-929392-78-7},
|
||||
year = {2003},
|
||||
OPTkey = { },
|
||||
OPTvolume = {},
|
||||
OPTnumber = {},
|
||||
OPTseries = {Embedded Systems},
|
||||
OPTaddress = {},
|
||||
OPTedition = {1st},
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||||
OPTmonth = {},
|
||||
OPTnote = {},
|
||||
OPTannote = {},
|
||||
OPTurl = {www.rtcbooks.com},
|
||||
OPTdoi = {},
|
||||
OPTissn = {},
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||||
OPTlocalfile = {},
|
||||
OPTabstract = {}
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||||
};
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||||
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@Article{article,
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author = {dd},
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title = {dd},
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journal = {dd},
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year = {2008},
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OPTkey = {},
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||||
OPTvolume = {},
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||||
OPTnumber = {},
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||||
OPTpages = {1,2},
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||||
OPTmonth = {JAN},
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||||
OPTnote = {},
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||||
OPTannote = {},
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||||
OPTurl = {},
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||||
OPTdoi = {},
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||||
OPTissn = {},
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||||
OPTlocalfile = {},
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||||
OPTabstract = {}
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||||
};
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||||
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||||
@Book{sqlite,
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author = {Micheal Owens},
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||||
title = {The definitive guide to SQLite},
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||||
publisher = {Apres ISBN 1-59059-673-0},
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||||
year = {2006},
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||||
OPTkey = {},
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||||
OPTvolume = {},
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||||
OPTnumber = {},
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||||
OPTseries = {Databases/SQLite},
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||||
OPTaddress = {},
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||||
OPTedition = {},
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||||
OPTmonth = {},
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||||
OPTnote = {},
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||||
OPTannote = {},
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||||
OPTurl = {},
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||||
OPTdoi = {},
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||||
OPTissn = {},
|
||||
OPTlocalfile = {},
|
||||
OPTabstract = {}
|
||||
};
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||||
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||||
BIN
pt100/pt100.dia
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BIN
pt100/pt100.dia
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BIN
pt100/pt100.jpg
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BIN
pt100/pt100.jpg
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pt100/pt100.tex
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pt100/pt100.tex
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\documentclass[a4paper,10pt]{article}
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\usepackage[utf8x]{inputenc}
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\usepackage{graphicx}
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\usepackage{fancyhdr}
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\usepackage{lastpage}
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\clubpenalty=300
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\widowpenalty=300
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%
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% Make the revision and doc number macro's then they are defined in one place
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\newcommand{\rev}{PA5}
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\newcommand{\etcdoc}{ HR222975 }
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\newcommand{\wlc}{{Water~Level~Controller~Unit}}
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\newcommand{\ft}{{\em 4 $\rightarrow$ 20mA } }
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\newcommand{\tds}{TDS Daughterboard}
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\newcommand{\oc}{$^{o}{C}$}
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\newcommand{\adctw}{{${\mathcal{ADC}}_{12}$}}
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\newcommand{\adcten}{{${\mathcal{ADC}}_{10}$}}
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\newcommand{\ohms}[1]{\ensuremath{#1\Omega}}
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\title{TDS Daughter Board Design Notes \\ \etcdoc revision \rev}
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\author{R.P. Clark}
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\begin{document}
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\pagenumbering{roman}
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\pagestyle{fancy}
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\maketitle
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\lhead{}
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\chead{\textbf{ETC6211: Total Dissolved Solids Daughterboard}}
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\rhead{}
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\rfoot{\thepage}
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\cfoot{}
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\lfoot{\textbf{\small ETC Document Number: \etcdoc Revision: \rev}}
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\maketitle
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\begin{abstract}
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The PT100, or platinum wire \ohms{100} sensor is
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a wisely used industrial temperature sensor that is
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are slowly replacing the use of thermocouples in many
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industrial applications below 600\oc, due to high accuracy\cite{aoe}.
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This chapter looks at the most common configuration, the
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four wire circuit, and analyses it from an FMEA perspective twice.
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Once considering single faults (cardinality constrained powerset of 1) and then again, considering the
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possibility of double simultaneous faults (cardinality constrained powerset of 2).
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The analysis is performed using Propositional Logic
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diagrasms to aid in the reasoning process, which takes
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the failure modes of the components, and produces a
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failure mode model for the circuit as a whole.
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Thus after the analysis the PT100 temperature sensing circuit, may be veiwed
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from an FMEA persepective as a component itsself, with a set of know failure modes.
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\end{abstract}
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\section{Overview of PT100 four wire circuit}
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The PT100 four wire circuit consists of teo resistors supplying
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a current to a third, the thermistor or PT100. By measuring volatges
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from sections of this circuit forming potential dividers, we can determine the
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current resistance of the platinum wire sensor. The resistance
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of this is directly related to temperature, and may be determined by
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look-up tables or a suitable polynomial expression.
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\subsection{Accuracy despite variable resistance in cables}
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For electronic and accuracy reasons the four wire circiut is used
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because of resistance in the cables. Resitance from the supply
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causes a slight voltage
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drop in the supply to the PT100. As no significant current
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is carried by the two `sense' lines the resistance back to the ADC
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causes only a negligible voltage drop. The current flowing though the
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whole circuit can be measured on the PCB by reading a third
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sense voltage from one of the load resistors. Knowing the current flowing
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through the circuit
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and knowing the voltage drop over the PT100, we can calculate its
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resistance by ohms law $V=I.R$, $R=\frac{I}{V}$.
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Thus a little loss of supply current due to resistance in the cables
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does not impinge on accuracy.
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The resistance to temperature conversion is achieved
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through the published PT100 tables\cite{eurothermtables}.
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\section{Safety case for 4 wire circuit}
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This sub-section looks at the behaviour of the PT100 four wire circuit
|
||||
for the effects of component failures.
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||||
All components have a set of known `failure modes'.
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||||
In other words we know that a given component can fail in several distict ways.
|
||||
Studies have been published which list common component types
|
||||
and their sets of failure modes, often with MTTF statistics \cite{mil1991}.
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||||
Thus for each component, an analysis is made for each of it failure modes,
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||||
with respect to its effect on the
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||||
circuit. Each one of these scenarios is termed a `test case'.
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||||
The resultant circuit behaviour for each of these test cases is noted.
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The worst case for this type of
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||||
analysis would be a fault that we cannot detect.
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Where this occurs a circuit re-design is probably the only sensible course of action.
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||||
\subsection{Single Fault FMEA Analysis of PT100 Four wire circuit}
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||||
\label{fmea}
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||||
Looking at this circuit, it simply consists of three resistors.
|
||||
Resistors according to the DOD Electronic component fault handbook
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||||
1991, fail by either going OPEN or SHORT circuit \cite{mil1991}.
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||||
%Should wires become disconnected these will have the same effect as
|
||||
%given resistors going open.
|
||||
For the purpose of his analyis;
|
||||
$R_{1}$ is the \ohms{2k2} from 5V to the thermistor,
|
||||
$R_p$ is the PT100 thermistor and $R_{2}$ connects the thermistor to ground.
|
||||
|
||||
\begin{table}[ht]
|
||||
\caption{PT100 FMEA Single Faults} % title of Table
|
||||
\centering % used for centering table
|
||||
\begin{tabular}{||l|c|c|l|l||}
|
||||
\hline \hline
|
||||
\textbf{Test} & \textbf{Result} & \textbf{Result } & \textbf{General} \\
|
||||
\textbf{Case} & \textbf{sense +} & \textbf{sense -} & \textbf{Symtom Description} \\
|
||||
% R & wire & res + & res - & description
|
||||
\hline
|
||||
\hline
|
||||
$R_1$ SHORT & High & - & Value Out of Range Value \\ \hline
|
||||
$R_1$ OPEN & Low & Low & Both values out of range \\ \hline
|
||||
\hline
|
||||
$R_p$ SHORT & Low & High & Both values out of range \\ \hline
|
||||
$R_p$ OPEN & High & Low & Both values out of range \\ \hline
|
||||
\hline
|
||||
$R_2$ SHORT & - & Low & Value Out of Range Value \\
|
||||
$R_2$ OPEN & High & High & Both values out of range \\ \hline
|
||||
\hline
|
||||
\end{tabular}
|
||||
\label{ptfmea}
|
||||
\end{table}
|
||||
|
||||
From table \ref{ptfmea} it can be seen that any component failure in the circuit
|
||||
will cause a common symptom, that of one or more of the values being out of range.
|
||||
So by defining an acceptable measurement/temperature range, and ensuring the
|
||||
values are always within these bounds we can be confident that none of the
|
||||
resistors in this circuit has failed.
|
||||
|
||||
\subsection{Single Fault Modes as PLD}
|
||||
|
||||
% Place in PLD diagram
|
||||
|
||||
\subsection{Range and PT100 Calculations}
|
||||
|
||||
PT100 resistors are designed to
|
||||
have a resistance of ohms{100} at 0 \oc \cite{eurothermtables}.
|
||||
A suitable `wider than to be expected range' was considered to be {-100\oc} to {300\oc}.
|
||||
According to the Eurotherm PT100
|
||||
tables \cite{eurothermtables}, this corresponded to the resistances \ohms{60.28}
|
||||
and \ohms{212.02} respectively. From this the potential divider circuit can be
|
||||
analysed and the maximum and minimum acceptable voltages determined.
|
||||
These can be used as bounds results to apply the findings from the
|
||||
PT100 FMEA analysis in section \ref{fmea}.
|
||||
|
||||
As the PT100 forms a potential divider with the \ohms{2k2} load resistors,
|
||||
the upper and lower readings can be calculated thus:
|
||||
|
||||
$$ highreading = 5V.\frac{2k2+pt100}{2k2+2k2+pt100} $$
|
||||
$$ lowreading = 5V.\frac{2k2}{2k2+2k2+pt100} $$
|
||||
|
||||
To convert these to twelve bit ADC (\adctw) counts:
|
||||
|
||||
$$ highreading = 2^{12}.\frac{2k2+pt100}{2k2+2k2+pt100} $$
|
||||
$$ lowreading = 2^{12}.\frac{2k2}{2k2+2k2+pt100} $$
|
||||
|
||||
|
||||
\begin{table}[ht]
|
||||
\caption{PT100 Maximum and Minimum Values} % title of Table
|
||||
\centering % used for centering table
|
||||
\begin{tabular}{||c|c|c|l|l||}
|
||||
\hline \hline
|
||||
\textbf{Temperature} & \textbf{PT100 resistance} &
|
||||
\textbf{Lower} & \textbf{Higher} & \textbf{Description} \\
|
||||
\hline
|
||||
{-100 \oc} & {\ohms{68.28}} & 2.46V & 2.53V & Boundary of \\
|
||||
& & 2017\adctw & 2079\adctw & out of range LOW \\ \hline
|
||||
{0 \oc} & {\ohms{100}} & 2.44V & 2.56V & Mid Range \\
|
||||
& & 2002\adctw & 2094\adctw & \\ \hline
|
||||
{+300 \oc} & {\ohms{212.02}} & 2.38V & 2.62V & Boundary of \\
|
||||
& & 1954\adctw & 2142\adctw & out of range HIGH \\ \hline
|
||||
\hline
|
||||
\end{tabular}
|
||||
\label{ptbounds}
|
||||
\end{table}
|
||||
|
||||
Table \ref{ptbounds} gives ranges that determine correct operation. In fact it can be shown that
|
||||
for any single error (short or opening of any resistor) this bounds check
|
||||
will detect it.
|
||||
|
||||
%\vbox{
|
||||
%\subsubsection{Calculating Bounds: High Value : HP48 RPL}
|
||||
%
|
||||
%
|
||||
%HP RPL calculator program to take pt100 resistance
|
||||
%and convert to voltage and {\adctw} values.
|
||||
%
|
||||
%\begin{verbatim}
|
||||
%<< -> p
|
||||
% <<
|
||||
% p 2200 + 2200 2200 + p + / 5 * DUP 5
|
||||
% / 4096 *
|
||||
% >>
|
||||
%>>
|
||||
%\end{verbatim}
|
||||
%}
|
||||
%
|
||||
%\vbox{
|
||||
%\subsubsection{Calculating Bounds: LOW Value : HP48 RPL}
|
||||
%
|
||||
%
|
||||
%HP RPL calculator program to take pt100 resistance
|
||||
%and convert to voltage and {\adctw} values.
|
||||
%
|
||||
%\begin{verbatim}
|
||||
%<< -> p
|
||||
% <<
|
||||
% p 2200 2200 p 2200 + + / 5 * DUP 5
|
||||
% / 4096 *
|
||||
% >>
|
||||
%>>
|
||||
%\end{verbatim}
|
||||
%}
|
||||
%
|
||||
%\subsection{Implementation of Four Wire Circuit}
|
||||
%
|
||||
%A standard 4 wire PT100\cite[pp 992]{aoe} circuit is read by
|
||||
%ports on the 12 bit ADC of the PIC18F2523\cite{pic18f2523}.
|
||||
%Three readings are taken. A reading to confirm the voltage level
|
||||
%over $R_2$ is taken,
|
||||
%from which the current can be determined.
|
||||
%The two sense lines then give the voltage over the PT100 thermistor.
|
||||
%As we know the current flowing through it we can determine the
|
||||
%resistance.
|
||||
%
|
||||
%After verification (PT100 voltages/readings in range etc) the temperature
|
||||
%value is determined by interpolation via the PT100 tables \cite{eurothermtables}.
|
||||
%First order low pass filtering is then applied to smooth the value.
|
||||
%\section{Water Level Readings - \ft Inputs}
|
||||
%\label{wl}
|
||||
%After h/w revision 0.4, water level sensor \ft connections are wired to the TDS daughterboard,
|
||||
%but are passed to the main unit via a multiplexer, and connect to the
|
||||
%14 pin harwin (to PIN 13 of JP1 \cite{pcbAI222562}).
|
||||
%
|
||||
%The safety critical \ft water~level readings are thus handled in the \wlc.
|
||||
%
|
||||
|
||||
\subsection{Single Fault FMEA Analysis of PT100 Four wire circuit}
|
||||
typeset in {\Huge \LaTeX} \today
|
||||
|
||||
Loading…
Reference in New Issue
Block a user