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Need assistance for OP AMP -20 to +200C
von Ivica L. (Company: Home) (laco)

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I've created in NI Multisim 11 project PT1000 and OP Amp TLC271CP for 
measuring temperature from-20C to +200 C. It should formula for 
calculation Vout and to check whether this model can work in reality. I 
am not electrician but my Hobby's electronics. Intervals Vout (ADC) is 
0-5 V. Microcontroller was ATMega 16, but that does not meet, if 
resolution ADC ATMega 16 is not good I think to use SPI MCP3201 12-bit 
ADC.  Further should formula for calculation RT (R7) on bases Vout.

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Re: Need assistance for OP AMP -20 to +200C
von MaWin (Guest)

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921.6Ω -> 0V and 1758.6Ω -> 5V

Formulas for this circuit see:

http://www.maxim-ic.com/app-notes/index.mvp/id/3450
http://www.umnicom.de/Elektronik/Schaltungssammlung/Temperatur/Pt1000/Pt1000.html

The TLC271 ist not a precision OpAmp, even with 0.0001% resistors
the deviation may be up to -5C to +5C of real temperature.

Better use an OpAmp with Vos below 1mV.

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