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LMP91000: O2-A2 of alphasense

Kai Hsiao
Guru 12675 points
Part Number: LMP91000

Dear Sir 

If I use O2-A2 of alphasense

1. May I know how to set A1 amp for O2-A2 ? I don't know what output voltage is correct

2. May I know what's the condition I need set Bias_sign to negative or positive (Should I refer to O2-A2's SPEC ,due to i don't see anything in this datasheet)

3. When should I need to turn-off (short) the FET ?

  • 0
    TI__Expert 5695 points
    TI Support team will contact you shortly.
  • 0 in reply to Jose Arteaga4
    TI__Intellectual 1960 points

    Dear Kai Hsiao

    Alphasense O2-A2 sensor is a 2 lead sensor.

    In this case LMP91000 has to be configured in the 2-lead galvanic cell potentiostat configuration (LMP91000 datasheet - Page 19 - figure 26)

    A1 is in buffer configuration.

    Setting examples:

    Vref devider can be set to 67% INT_Z = '10'

    Variable bias can be set to zero BIAS = '0000'

    BIAS_SIGN can be left '0' because the are not adding BIAS to the sensor.

    Regards

    Massimo

  • 0 in reply to Massimo Mascotto
    Guru 12675 points

    Dear Massimo 

    Sorry!! I made a typo 

    I refer to 3 Lead Alphasense CO-AF in GasSensorEVM

    1. May I know what's the condition I need to set BIAS_SIGN to 1?? I mean the sensor datasheet will have this information??

    2. What's the condition I need to turn-off (short) the internal FET or in your experience ,the FET never turn off

    Thanks

  • 0 in reply to Kai Hsiao
    TI__Intellectual 1960 points

    Dear Kai Hsiao

    1. May I know what's the condition I need to set BIAS_SIGN to 1?? I mean the sensor datasheet will have this information??

    There are several kind of electrochemical sensors. Some of them doesn't required any bias (polarization between RE and WE), while others may required a voltage between the RE and WE).

    The required polarization (bias) could be negative (WE > RE) or positive (RE>WE). To address any possible conditions LMP91000 has to be configured using INT_Z, BIAS_SIGN, BIAS.

    INT_Z defines the percentage of the Vref that is applied to WE

    BIAS defines the percentage of Vref that will be applied between WE and RE

    BIAS_SIGN define if the BIAS is positive or negative.

    I guess that CO-AF is a zero bias. It means that BIAS is 0%Vref and BIAS_SIGN is a don't care.

     

    2. What's the condition I need to turn-off (short) the internal FET or in your experience ,the FET never turn off

    In case of zero bias sensor, to save power is possible to short the internal FET and put the LMP91000 in deep sleep (OP_MODE = '000')

    In this way the LMP91000 consumes small amount of current and the zero bias polarization is kept shorting the internal FET.

    Regards

    Massimo