Post by thread:Thermo Couple Interface

Gday all, I have a need to interface a thermo couple to a pic, I believe that there is a special purpose ic out there that not only scales but also corrects the output to allow for nonlineararity and presents you with a voltage/temp value or better still I2C of SPI. Anybody know its name/manufacture? Thanks -- Lee McLaren spam_OUTlmclarenTakeThisOuTtrumpet.com.au Comstra pty. ltd. .....lmclarenKILLspam@spam@comstra.com.au 2 Kirksway place phone 03 62244488 Hobart Tasmania fax 03 62244601 Australia 7000 mobil 018 138682 'It was five hours of Boggs's "channelling". After three hours I asked him to summon up the soul of Jimi Hendrix and requested All Along the Watchtower. You know, the guy's been dead twenty years but he still hasn't lost his edge' Mulder

> > Gday all, > I have a need to interface a thermo couple to a pic, I believe that > there is a special purpose ic out there that not only scales but also > corrects the output to allow for nonlineararity and presents you with a > voltage/temp value or better still I2C of SPI. > Anybody know its name/manufacture? > > Thanks > -- > Lee McLaren lmclarenKILLspamtrumpet.com.au > Lee, Analog devices AD594/AD595 depending on flavor of TC, J/K respectivly. Not I2C or SPI, but still nice parts. Brian --

Brian Read wrote: {Quote hidden}> > > > > Gday all, > > I have a need to interface a thermo couple to a pic, I believe that > > there is a special purpose ic out there that not only scales but also > > corrects the output to allow for nonlineararity and presents you with a > > voltage/temp value or better still I2C of SPI. > > Anybody know its name/manufacture? > > > > Thanks > > -- > > Lee McLaren .....lmclarenKILLspam.....trumpet.com.au > > > Lee, > > Analog devices AD594/AD595 depending on flavor of TC, J/K respectivly. > Not I2C or SPI, but still nice parts. > > Brian > > -- Thankyou for the info. Regards -- Lee McLaren EraseMElmclarenspam_OUTTakeThisOuTtrumpet.com.au Comstra pty. ltd. lmclarenspam_OUTcomstra.com.au 2 Kirksway place phone 03 62244488 Hobart Tasmania fax 03 62244601 Australia 7000 mobil 018 138682 'It was five hours of Boggs's "channelling". After three hours I asked him to summon up the soul of Jimi Hendrix and requested All Along the Watchtower. You know, the guy's been dead twenty years but he still hasn't lost his edge' Mulder

Analog Devices used to make a chip like that. I think it was an AD590. It did cold junction compensation and gave a linear voltage output for the temperature. At 06:53 PM 3/5/97 +1100, lmclaren wrote: {Quote hidden}>Gday all, >I have a need to interface a thermo couple to a pic, I believe that >there is a special purpose ic out there that not only scales but also >corrects the output to allow for nonlineararity and presents you with a >voltage/temp value or better still I2C of SPI. >Anybody know its name/manufacture? > >Thanks >-- >Lee McLaren @spam@lmclarenKILLspamtrumpet.com.au >Comstra pty. ltd. KILLspamlmclarenKILLspamcomstra.com.au >2 Kirksway place phone 03 62244488 >Hobart Tasmania fax 03 62244601 >Australia 7000 mobil 018 138682 > >'It was five hours of Boggs's "channelling". After three hours >I asked him to summon up the soul of Jimi Hendrix and requested >All Along the Watchtower. You know, the guy's been dead >twenty years but he still hasn't lost his edge' >Mulder > > Larry G. Nelson Sr. RemoveMEL.NelsonTakeThisOuTieee.org http://www.ultranet.com/~nr

lmclaren <spamBeGonelmclarenspamBeGoneTRUMPET.COM.AU> wrote: > I have a need to interface a thermo couple to a pic, I believe that > there is a special purpose ic out there that not only scales but also > corrects the output to allow for nonlineararity and presents you with a > voltage/temp value or better still I2C of SPI. > Anybody know its name/manufacture? If you just need a temperature sensor but not necessarily a thermocouple, you could use the National Semiconductor LM75. It is a temperature sensor in an 8 pin SO package with an I2C interface, it costs around US $1.60 in hundred lots, and there's a free demo board available: http://www.national.com/pf/LM/LM75.html Cheers, Eric

At 05:29 PM 06/03/1997 -0500, you wrote: >Analog Devices used to make a chip like that. I think it was an AD590. It >did cold junction compensation and gave a linear voltage output for the >temperature. > Sorry no. AD590 is an expensive but fairly accurate temeprature sensing device that outputs 10 uA per degree Kelvin. A thermocouple needs Cold Junction Compensation and linearization in order to properly function. ie: The thermocouple wire is brought to a connector block that that has a temperature sensor connected to it (like an AD590). Then the voltage is measured and put into a polynomial to determine the actual temperature measured at the other end of the thermocouple wire. Easiest way to do the CJ compensation is to use the LT1025 from Linear Technologies. Set a jumper for whcih type of thermocouple you are using and make it physically close to your terminal block and Voila` It gives you the value you need for K or J or T type thermocouples. For a really good description on how to use thermoouples get an OMEGA catalog. It's the definitive description and has all the tables you need. Regards, John Pioneers are the ones, face down in the mud, with arrows in their backs. Automation Artisans Inc. Ph. 1-250-544-4950 PO Box 20002 Fax 1-250-544-4954 Sidney, BC CANADA V8L 5C9