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Looking for a low-power op-amp for MG811 CO2 sensor

Hang Lee YUEN
Prodigy 55 points
Other Parts Discussed in Thread: MSP430F5529

I am trying to make a CO2 sensor system basically through the microcontroller and CO2 sensor.

The MG811 CO2 sensor and MSP430F5529 microcontroller are in used in my case. 

I am using MSP430F5529 microcontroller and the ADC12 function, it suggests the internal reference voltage which is 2.5V for the low-power purpose.

For my simple test for the CO2 sensor while input 5.08V power and the output voltage is from 10mV to 900mV.

So I am looking for an op-amp which can convert 10 - 900mV signal to around 2.5V. 

Anything else should I consider? And any op-amp is suitable in my case?

PS the specification of MG811 CO2 sensor.

Thanks!

  • 0
    TI__Expert 6275 points

    There are many design considerations that can be analyzed up front to ensure your first PCB will be accurate as possible.

    Besides the op amp there may need to be an R-C filter so that when the internal sampling capacitor of the ADC connects there is an accurate transfer of the input signal during the tsampl time.

    The following questions answered by you will help me to recommend the best choices:

    1) Any single supply op amp is usually only accurate in a linear range 100mV away from either supply rail.  What power supply is available for the op amp?

    So if power supply for op amp is greater than 2.6V input to ADC could be scaled from 100mV to 2.5V.

    2) Is the internal ADC reference available to the outside world?

    3) Is there any accurate reference voltage available for scaling?

    4) In your MSP430, when you are reading the sensor what is the sample time (tsmpl) and time between samples?  i.e. tsmpl = 1us and 100us between tsmpl

    5) What small signal closed loop bandwidth do you need on your sensor signal?

    6) What is the fastest rate of change on your sensor signal (how many seconds to go from 10mV to 900mV)?