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user17592
user17592

I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component count and manual calibration time is not an issue.

It's a K type thermocouple (41uV/ºC) and I'm hoping for an accuracy of around 25ºC from 100ºC to 1000ºC. 1 sample per second is plenty. The ADC is 10 bit, and there is a regulated 12v, 5v, 3.3v and ground supply.

Could it be more economical with the above requirements to use cheap op-amps instead of a purpose made instrumentation amp?

As I understand, the problem with cheap op-amps is their input offset voltage and drift. But am I correct in saying:

  • Many cheap op-amps can be offset-nulled with a variable resistor?
  • and the offset drift is relatively negligible even for a thermocouple? (15uV/ºC in the LM741)

If so, the question remains what circuit could be used. Would 3 op-amps be necessary? or could it be done with fewer?

Last but not least, suggestions for which op-amp would be appreciated.

Thanks! I know I'm asking a lot here.

I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component count and manual calibration time is not an issue.

It's a K type thermocouple (41uV/ºC) and I'm hoping for an accuracy of around 25ºC from 100ºC to 1000ºC. 1 sample per second is plenty. The ADC is 10 bit, and there is a regulated 12v, 5v, 3.3v and ground supply.

Could it be more economical with the above requirements to use cheap op-amps instead of a purpose made instrumentation amp?

As I understand, the problem with cheap op-amps is their input offset voltage and drift. But am I correct in saying:

  • Many cheap op-amps can be offset-nulled with a variable resistor?
  • and the offset drift is relatively negligible even for a thermocouple? (15uV/ºC in the LM741)

If so, the question remains what circuit could be used. Would 3 op-amps be necessary? or could it be done with fewer?

Last but not least, suggestions for which op-amp would be appreciated.

Thanks! I know I'm asking a lot here.

I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component count and manual calibration time is not an issue.

It's a K type thermocouple (41uV/ºC) and I'm hoping for an accuracy of around 25ºC from 100ºC to 1000ºC. 1 sample per second is plenty. The ADC is 10 bit, and there is a regulated 12v, 5v, 3.3v and ground supply.

Could it be more economical with the above requirements to use cheap op-amps instead of a purpose made instrumentation amp?

As I understand, the problem with cheap op-amps is their input offset voltage and drift. But am I correct in saying:

  • Many cheap op-amps can be offset-nulled with a variable resistor?
  • and the offset drift is relatively negligible even for a thermocouple? (15uV/ºC in the LM741)

If so, the question remains what circuit could be used. Would 3 op-amps be necessary? or could it be done with fewer?

Last but not least, suggestions for which op-amp would be appreciated.

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Jayy
Jayy
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Economical thermocouple amplifier circuit

I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component count and manual calibration time is not an issue.

It's a K type thermocouple (41uV/ºC) and I'm hoping for an accuracy of around 25ºC from 100ºC to 1000ºC. 1 sample per second is plenty. The ADC is 10 bit, and there is a regulated 12v, 5v, 3.3v and ground supply.

Could it be more economical with the above requirements to use cheap op-amps instead of a purpose made instrumentation amp?

As I understand, the problem with cheap op-amps is their input offset voltage and drift. But am I correct in saying:

  • Many cheap op-amps can be offset-nulled with a variable resistor?
  • and the offset drift is relatively negligible even for a thermocouple? (15uV/ºC in the LM741)

If so, the question remains what circuit could be used. Would 3 op-amps be necessary? or could it be done with fewer?

Last but not least, suggestions for which op-amp would be appreciated.

Thanks! I know I'm asking a lot here.