Some applications may not require continuous sampling and may only need a finite number of samples to be available at read.

This means that if you read 30000 Samples in the DAQmx Read function in the acquisition loop, there will be 30.03 samples being accumulated in the buffer every iteration.Īdditional Troubleshooting Considerations: For example, this is common with M Series cards if you chose a sample rate that they can't achieve exactly, like 30000 S/s, the card will run at 30030.03 S/s. Otherwise, there could be an overflow error because there will be some samples that are not being read and will be accumulated in the buffer. Note: Remember always to read back the Sample Rate of each task by using a DAQmx Timing property node > SampClk.Rate. This is important to confirm that the Actual Sample rate used by the card is exactly what the user specified. Each DAQmx Read will take 1s, so the buffer won't fill up every iteration. For example, one task reads 3000 Samples / 3000 Samples/s = 1s, and the second task in the loop reads 100 Samples / 100Samples/s = 1s.

Make sure each DAQmx Read in the loop has the same read rate.

One DAQmx read will take longer to read the same number of samples, while that longer read is occurring the other task's buffer is filling up. The reason that this error presents itself is that the DAQmx read is a blocking call. This error can occur if two tasks sharing an acquisition loop have different sample rates. However, if the error is occurring because data is not being readout of the DAQmx buffer fast enough (Case 1 above), increasing the buffer size will only delay the occurrence of the error, and will not eliminate it completely.Ĭase 3: Reading two tasks running at different rates, using one acquisition loop Occasionally, this error can be resolved by simply increasing the size of the host side data buffer manually. Note: Do not use Highlight Execution with code that contains a DAQmx Read, since it will slow down the execution and cause a buffer overflow.Ĭase 2: PC Buffer Is Too Small to Hold Task DataĪnother reason for this error is that the DAQmx PC Buffer is too small to hold the amount of data required by the DAQmx task, causing an overwrite in the DAQmx PC Buffer before data has been acquired at all. If increasing the while loop performance is not an option, you may need to lower the sample rate for your application instead.

If the while loop is performing more slowly than expected, you may need to implement a Producer/Consumer architecture to move other processes, such as logging, post-processing, analysis, and user interface functionality outside of the acquisition loop. Note: DAQmx Read will automatically wait until the requested number of samples are available, so it is usually only necessary to control one of these factors in a particular application.

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