Error -200019: ADC Conversion Attempted Before Prior Conversion Was Complete

Updated Jun 27, 2019

Reported In

Driver

  • NI-DAQmx

Other

Applies to All NI Hardware with an ADC

Issue Details

  • Why do I get error -200019 when I increase the rate of my DAQmx task?
  • My task will not run because of error -200019.
  • I am using an external clock to sample an analog input. When I sample the data at a lower rate, everything works as expected. When I increase the frequency of the external clock, I receive error -200219.
  • I receive error -200019 when I use an external clock to sample an analog input, even though the clock runs at a rate within the specification of the device.
Error -200019: ADC Conversion was attempted before prior conversion was completed

Solution

Even if the clock is external, the rate specified in the task configuration determines the buffer size and other task parameters. To keep from overwriting the data, the rate must be set to the greatest expected clocking frequency. The following can be possible solutions for error -200019:
  • Reduce the sampling rate to allow the ADC more time to make the conversion.
  • Check the specifications for your device and make sure the sampling rate is less than the maximum allowed sample rate.
  • Increase the timeout value on the DAQmx Read VI.
  • If you're using an external clock, make sure to check the integrity of the external clock signal either by visualizing it on a scope or on an input on the DAQ device itself. If the edges of this external signal have glitches or noise, this can cause sampling to occur more often, as glitches in a single edge can be misidentified as being multiple edges. This will cause more samples to be read and more ADC conversions to take place, which can lead to this error.
    • If you're using PFI as input terminal for the external clock, you can try connecting digital ground (D GND) to the ground of the clock sourcing device to reduce noise on the clock signal.
  • If these steps don't resolve the error, try resetting the NI MAX database. This will remove potential corruption within DAQmx tasks, and the required reboot will force any running tasks to stop.

Additional Information

Error -200019 occurs any time the ADC is requested to convert the analog signal to a digital representation before the current conversion is completed.  The ADC has a conversion rate that the sample clock cannot exceed.

Note: Simultaneous sampling cards will have one maximum sampling rate no matter how many channels are used. Non simultaneously sampled (multiplexed) cards will have a maximum sample rate that is dependent on how many channels are being sampled. For example, an aggregate sample rate of 250 kS/s when acquiring 4 channels of data results in a maximum sample rate of 250/4 = 62.5 kS/s per channel:
 
Simultaneous Sampled Example:

NI 4472 Sampling Specifications

Aggregate Sampled Example:

NI 632X Sampling Specifications

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