Problems with the PCI-6024E and PCI-6025E in VirtualBench-Function Generator Primary Software: Other NI Software>>VirtualBenchPrimary Software Version: 2.51 Primary Software Fixed Version: N/A Secondary Software:
Problem: I am using a Low Cost PCI E Series DAQ Board (PCI-6024E or PCI-6025E) and VirtualBench-Function Generator to generate sine waves and square waves. I configure the wave the way I want it, and then I press the On button. I see the waveform being generated on my output for just a short time (about 1 to 3 seconds), and then the output goes to zero and stays there. I don't get a warning or an error message from VirtualBench-FG and all the settings appear the same, but the output just stops. If I turn off the On button and then turn it on again, the same thing will happen. If I generate a square wave, the same thing happens, but it takes a little longer to occur. Solution: This problem is related to the analog output capabilities of the 6024E and the 6025E. They are able to generate analog outputs at a maximum rate of 10 kS/s (kiloSamples/second) with DMA (direct memory access) or 1 kS/s with IRQ (interrupt request), but since they have no onboard memory to store incoming waveform information, both these specifications are system dependent. VirtualBench-Function Generator uses DMA transfers and the default update rate in the Settings for these boards is 10 kS/s. Since these update rates are system dependent, they vary depending on the PCI controller chipset, the amount of traffic on the PCI bus, and the overall performance of the system. If the system cannot maintain the waveform at the specified rate, then it will stop being generated. To avoid this problem, you can uncheck the option in Edit >> Settings to use the "Recommended Update Rate" and change the update rate from 10 kS/s to something smaller -- 1 kS/s is a good place to start, but you can try different values until you find an update rate that your system can consistently support. The drawback is that the smaller this number is, the smaller the frequency of the waveform that you can generate. Working with the Buffer Size setting will also allow you to tweak the waveform's frequency. If you use the board in a different system, then you may be able to generate faster waveforms. Standard E Series boards have analog output rates that are not system dependent, because they each have an onboard FIFO (first in first out) buffer, which can generate waveforms at a rate of 1 MS/s (megaSamples/second), regardless of the system. Related Links: Attachments:
Report Date: 07/13/1999 Last Updated: 02/14/2003 Document ID: 1NC7BQTS |
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