User`s guide

15 Frequently Asked Questions
previous ly calculated v alue of 0.25% , there is a di fference of 0.04% from the
expected value.
If you want to further refine the measured deviation for your hardware,
assume the following:
• Output board that generates a 50 Hz sine wave (expected signal)
• Sample time of 1/10200
• Measured signal of 50.002 Hz
1/10200 seconds X 1.193 x 10
6
ticks/seconds = 116.96 ticks
Round this number to the nearest whole number of 117 ticks. The resulting
frequency is then
(116.96 ticks/117)(50) = 49.983 Hz
The d iffere nce between the e xpected and measured signal is 0.019, which
deviates from the expected signal v alue by 0.038% (0.019/50.002). The
deviation when the sample time is 1/10000 is 0.04%.
Some amount of error is common for most PCs, and the margin of error varies
frommachinetomachine.
Note Most high-level operating systems, like Microsoft Windows or Linux
®
,
occasionally insert extra long intervals to compensate for errors in the timer.
Be aware that the xPC Target software does not attempt to compensate for
timererrors. Thisisbecauseforthisproduct, close repeatability is more
important for most models than exact timing. However, some chips migh t
have inherent designs that produce residual jitters that could affect your
system. For example, some Pentium chips might produce residual jitters on
the order of 0.5 microsecond from interrupt to interrupt.
Why Did I Get Er ror -10: Invalid File ID on the Target
PC?
You might get this error if you are acquiring signal data with a scope of type
file. This error occurs because the size of the signa l data file exceeds the
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