Why Do I See Incorrect Output (Glitch) When Using the PCI-6723? Hardware: Signal Sources (AWG/FG/AO)>>Analog Output Devices>>PCI-6723
Problem: When I use the PCI-672x, I see a glitch in the signal, even when outputting a DC signal using buffered generation. You can see this when you use a test panel to output a sine waveform with amplitude of zero. What is wrong? Solution: This is expected behavior for the PCI-672x analog output boards. If you look in the specifications for the PCI-672x, you can find the specifications for this glitch listed as the channel-to-channel update glitch. It should be 70mV or less and no more then 1.2 microseconds wide. If viewing the analog output on a digital oscilloscope, it may appear that the glitch lasts far longer than the listed 1.2 microseconds. To view the glitch correctly, set the time/division to about 1 microsecond. This will ensure than the oscilloscope samples the signal at a high enough rate to capture its true frequencies. Setting a longer time/division reduces the sampling rate of the oscilloscope and causes it to alias the signal. In one instance, with a time/division of 25 ms, the glitch appeared to be as long as 100 ms. It is also important to note that the channel-to-channel update glitch still holds true when only using one channel. It is specifically the glitch that occurs with any update. The channel-to-channel update glitch also appears on every channel. A lowpass RC circuit should help this glitch. Another alternative is to build a reglitching circuit, or purchase a National Instruments analog output board with a built-in reglitching circuit. Related Links: KnowledgeBase 2TDC7TQ8: What is Glitch Energy? KnowledgeBase 0HGFNKBB: Reducing Glitches of Analog Output for MIO Boards Attachments:
Report Date: 06/07/2004 Last Updated: 08/09/2004 Document ID: 3A6GIJIO |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
