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ADS114S08: how to pause the measurements in a continuous mode

Slava Prokopii
Intellectual 2076 points
Part Number: ADS114S08
Other Parts Discussed in Thread: ADS1260

Hello.

We are going to develop a conductance meter for liquids.

To exclude a polarization of a measured liquid, we want to use a bipolar pulse train for current excitation in the liquid.

The frequency of excitation signal is in the range of 1...3 kHz.

The measurement will be done during the positive period of excitation pulse. So the measurement window is in the range of 500us .... 333us.

Each measurement has to be synchronized with a positive edge of excitation pulse.

Taking into account the conversion time of ADS114S08 working on 4ksps: for the first data - 461us, and for the next data in a sequence - 250us,

it is clear that we are not able to use single conversion mode in measurement window of 333us.

So the question is: is there a method to launch a continuous conversion mode, then hold the giving of the results until the next positive edge of excitation pulse will arrive to get the data in range of 250us after releasing?

  • 0
    TI__Guru** 113765 points

    Hi Slava,

    If you were to use just a continuous conversion mode, there would be no synchronization as to when the conversion starts/stops relative to the positive edge of the excitation pulse.  If you were to synchronize by either using the START/SYNC pin or the START command, you will still have the initial latency for the first conversion result.

    The only way to speed things up is to provide an external master clock, but the maximum clock frequency is 4.5MHz which would adjust the first conversion to be available at 419.5us which still does not get you to 330us.

    It may be possible to stop/start the external clock during continuous conversion mode.  Stopping the external clock would stop the ADC from converting and once the clock is reapplied the ADC will again begin to convert.  In theory this should work, but there is no way of knowing where in the conversion cycle the clock was stopped and what may be in the accumulator at the time which could mean there is data that can corrupt the conversion result.  So I would not recommend this approach.

    It would appear that you need a device with a higher data rate.  Perhaps the ADS1260/61?

    Best regards,

    Bob B