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k type thermocouple output voltage

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mohannad100

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k-type voltage

hi every body can i replace the followin amplifier circuit from max340 and all other compenent to lm741 ICS or lm324 to cinditioning circuit from mv to voltage that suite to ADC.
thanks.
 

thermalcouple output

mohannad100,
The short answer is "no". The reason is that the 741 op amp has an input offset voltage of 5 or 6 mV. The 324 has an input offset voltage of 7, 9, or 10 mV depending on the grade. Even if the offset voltage of the 741 is trimmed out, the typical offset voltage drift is 15uV/Deg C for the "A" grade. The drift spec is not given for lower grades, or for the LM324. Keeping in mind that the sensitivity of the type K thermocouple is about 40 uV/Deg C (See https://www.omega.com/temperature/z/pdf/z204-206.pdf), it is apparent that the offset voltage characteristics of the 741 and 324 are unacceptably high. The MAX430 has an input offset voltage of only 10 uV, and an input offset voltage drift of 0.05uV/Deg C.
Regards,
Kral
 

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