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What is Reglitching and How Do I Use it?

Hardware: Multifunction DAQ (MIO)>>E Series>>AT-MIO-16E-1, Legacy DAQ Devices>>Multifunction DAQ>>AT-MIO-16E-1

Problem:
The specifications in the user manual of my data acquisition (DAQ) board refer to a property called reglitching.  What is reglitching and how do I use it? 

Solution:
In normal operation, a DAQ board's digital to analog converter (DAC) will glitch whenever it is updated with a new value. The glitch energy differs from code to code and appears as distortion in the frequency spectrum.

Some National Instruments DAQ boards contain reglitching circuitry at the DACs that generate uniform glitch energy at every code transition rather than large glitches at the major code transitions. Notice that this reglitch circuit does not eliminate the glitches; it only makes them more uniform in size, resulting in a more uniform frequency spectrum.

On 12-bit analog output, reglitching is normally disabled at start-up and your software can independently enable each channel.
On 16-bit analog output, reglitching is always enabled.

The following devices support reglitching:
  • NI 6071E
  • NI 6070E (AT-MIO-16E-1, PCI-MIO-16E-1)
  • AT-MIO-16E-2
  • AT-MIO-64E-3
  • PXI-MIO-64E-1
  • VXI-MIO-64E-10
  • 671X devices
  • DAQCard-6062E
  • NI 6052E (16-bit analog output)
How to enable Reglitching:
  Traditional NI-DAQ NI-DAQmx
LabVIEW To enable reglitching in LabVIEW, use the AO Parameter VI located in the advanced analog output sub-palette. To enable reglitching in LabVIEW 7.0, use the DAQmx Channel Property Node located in DAQmx sub-palette.
NI-DAQ Function Calls To enable reglitching with NI-DAQ function calls use the AO_Change_Parameter function.

Here is the function declaration:

status = AO_Change_Parameter (deviceNumber, channel, paramID, paramValue)

The parameter ID is ND_REGLITCH, and the paramValue could be set to ND_OFF or ND_ON to disable or enable reglitching.		 To enable reglitching with NI-DAQmx function calls use the Reglitching Enable Property

Here are the declarations for getting, setting, and resetting the reglitch property:

int32 DllExport __CFUNC DAQmxGetAOReglitchEnable(TaskHandle taskHandle, const char channel[], bool32 *data);

int32 DllExport __CFUNC DAQmxSetAOReglitchEnable(TaskHandle taskHandle, const char channel[], bool32 data);

int32 DllExport __CFUNC DAQmxResetAOReglitchEnable(TaskHandle taskHandle, const char channel[]);
Visual Basic To enable reglitching in Visual Basic, use the CWDAQTools.AOParameter method to enable the reglitching.

Here is the function declaration:

CWDAQTools.AOParameter ( Device, ParamName, ChannelString, Operation, FloatIn, ValueIn, StringIn, BooleanIn, DeviceOut, ValueOut, FloatOut, StringOut, BooleanOut)

The relevant parameters are: Device, ParamName (should be set to cwaoReglitching), ChannelString, and BooleanIn (Set to TRUE to enable).		 N/A

Again, reglitching does not eliminate or reduce glitches.  If producing a glitch free, high performance, signal is important, refer to the National Instruments signal generators and DSA boards for analog output solutions.  See the related links below for more information regarding glitch energy and reducing glitches.

Related Links:
Product Manuals: E Series User Manual (February 2007)
KnowledgeBase 2TDC7TQ8: What is Glitch Energy?
KnowledgeBase 0HGFNKBB: Reducing Glitches on the Analog Output of MIO DAQ Devices
NI Signal Generators

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Report Date: 06/20/2002
Last Updated: 06/08/2009
Document ID: 2MJBBB8R

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