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Original question:

ADS1299-4: About resistance measurement function (LOFF(AC))

ADS1299-4: There is an OFFSET for a few seconds after the measurement is completed.

Ryu Yamashita
Genius 3705 points
Part Number: ADS1299-4

Tool/software:

Hi team,

Same design as this thread.
https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1503530/ads1299-4-about-resistance-measurement-function-loff-ac/5779950#5779950

The offset is added for a few seconds after the end of the measurement as shown below.
Is there a setting or method to turn this off immediately?

Best Regards,
Ryu.

  • +1
    TI__Guru 66466 points

    Hello Yamashita-san,

    Thank you for your post.

    Do you mean that, after turning off the AC lead impedance measurement, the customer wants the DC level to return to normal more quickly?

    I would suggest configuring the channel input MUX as internal-short (CHnSET[2:0] = 001b). This will short the PGA inputs together for that channel and drive them together to a known common-mode voltage. They can keep this setting for a short duration (i.e. maybe few hundred milliseconds), then change the setting back to 000b (Normal Electrode).

    Regards,

    Ryan