Why does VirtualBench-Logger Log Data Every 168 Seconds When I Specify a Larger Time Interval?Primary Software: Other NI Software>>VirtualBenchPrimary Software Version: 2.1 Primary Software Fixed Version: N/A Secondary Software: N/A
Problem: Using a E-Series DAQ board I specified a Time Interval Setting of 300 seconds (5 minutes) in the VirtualBench-Logger. However looking at my log file and timing the update rate on the screen, the data is actually being collected every 167.7 seconds. It seems that no matter what value I use the largest Time Interval I can have is 167.7 seconds. How can I get it to actually log at 300 seconds? Solution: This is a hardware limitation of your DAQ board. VirtualBench-Logger uses the Time Interval as the amount of time between scans ( inverse of the Scan Rate). So if your Time Interval is 10 seconds, your board will take one scan every 10 seconds and have a Scan Rate will be 0.1 scans per second. On an E-Series board the Scan Clock is a 24-bit counter and uses the internal 100 kHz timebase. The slowest clock signal that combination can produces is 0.00596 Hz or one pulse every 167.77 seconds ((2^24)/100000). For non E-Series boards this time may be longer or shorter depending on the timebase and the counter resolution. In order to increase your log rate, use the Time Interval and the Log Every settings to achieve the log rate you need. In the 300 seconds example you could use a Time Interval of 150 seconds and log to disk every 2 intervals or any combination that multiplies to 300. The Time Interval can be fractional but the Log Every x Intervals must be a whole number. It is also better to use the highest possible Time Interval, since it is hardware timed. Related Links: Attachments:
Report Date: 06/08/1999 Last Updated: 12/05/2004 Document ID: 1M7DMQTS |
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