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Digitizer Timeout in RIS Mode During Fetch Function



Primary Software: Driver Software>>NI-SCOPE
Primary Software Version: 3.8.6
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: Modular Instruments>>High-Speed Digitizers (Scopes)>>PCI-5152, Modular Instruments>>High-Speed Digitizers (Scopes)>>PXI-5152, Modular Instruments>>High-Speed Digitizers (Scopes)>>PXI-5153, Modular Instruments>>High-Speed Digitizers (Scopes)>>PXI-5154, Modular Instruments>>High-Speed Digitizers (Scopes)>>PCI-5153, Modular Instruments>>High-Speed Digitizers (Scopes)>>PCI-5154

Problem:
My digitizer is producing Error -1074126845 with Status Code -200221 in the fetch function while in Random Interleave Sampling (RIS) mode. What is the problem?

 

Error -1074126845

 



Solution:
This issue may occur when the device has not been self-calibrated according to the specifications given for the device. For instance, the PXI-5152, PXI-5153 and PXI-5154 devices must be self-calibrated every time the internal temperature changes 5 degrees for correct operation within that range. This is explained in the table at the bottom of the High-Speed Digitizers Help topic NI 5152/5153/5154 Calibration. Also, see the 5152/5153/5154 Calibration Procedure for more information about Self-Calibration. To query the device internal temperature using the NI-SCOPE driver, use the "Device Temperature" attribute through a property node in LabVIEW.

If a device is not self-calibrated, the root of the problem is that the Fetch function will not return until all the RIS bins are filled with data (see the Digitizer Sampling Methods Product Manual for more explanation). RIS Bins may not be filled with data if the device internal temperature drifts significantly without being self-calibrated. A walk-through of how this works is given on the High-Speed Digitizers Help topic here, Equivalent-Time Sampling and Random Interleaved Sampling. (At the bottom of this article, it explains that the RIS bins must be filled before the function returns its data.)
 
NI recommends that the device be self-calibrated according to the procedures given in the calibration manual mentioned above. However, in some use cases, you may be unable to implement a self-calibration and you may be willing to trade off specified performance with a software work-around. If you are willing to accept this risk, you may choose to look into modifying the following software option.

 

The NI-SCOPE attribute, Horizontal»RIS Method, can be set to allow for incomplete RIS bins. By default, this value is set to "Exact Number of Averages", which means all the bins must be filled with the exact number of averages specified or the Fetch function will not return until the specified timeout. When it times out, it will return an error. If you set this RIS Method to "incomplete", then the Fetch function will begin filling bins and averaging samples as usual; however, if the specified timeout elapses and all the bins are not filled, the Fetch function will now return, without error, and with whatever data is available. This is explained in the following Help Document, Horizontal:RIS Method Property. Again, the caveat with using the "incomplete" horizontal method is that some data maybe missing or less accurate, as it has not been averaged consistently.

Here is a rough comparison of the performance trade-off of a completed RIS average fetch (with self-calibration performed) vs. an incomplete RIS average fetch (without self-calibration). This was benchmarked using a 10 MHz input signal to a PXI-5152, which was sampling at 10 GS/s using the LabVIEW Example Finder example niScope EX Random Interleaved Sampling.vi

RIS Method = Exact Number of Averages (with self-calibration):

RIS Method = Incomplete (without self-calibration):

 


Related Links:
Product Manuals: Equivalent-Time Sampling and Random Interleaved Sampling
NI High-Speed Digitizers Help: Equivalent-Time Sampling and Random Interleaved Sampling
NI High-Speed Digitizers Help: Horizontal:RIS Method Property
Specifications Explained: NI Oscilloscopes and Digitizers

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Report Date: 08/16/2011
Last Updated: 10/04/2017
Document ID: 5OFB1P7G

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