Changing the trigger conditions with the Acquisition
Triggering dialog box also affects the Oscilloscope
Mode trigger conditions, and vice versa, even though the modes trigger
on different channels.
The trigger level is saved as a digital A/D
converter value, so the associated level in engineering units will change
if the channel gain is changed or the channel is re-calibrated.
There are some restrictions to the amount of
pre- and post-trigger data that can be acquired.
For 200 Series parallel
port instruments (i.e., DI-220, DI-222, and DI-221TC), the total number
of pre- and post-trigger data points times the number of enabled channels
must be an even number less than 8180.
(pre-trigger points + post-trigger points) × number of
enabled channels = (even number < 8180)
For plug-in board instruments,
the total number of pre- and post-trigger data points times the number
of enabled channels must be an even number less than the DMA input buffer
size (which is read by choosing Sample Rate from the Edit menu).
(pre-trigger points + post-trigger
points) × number of enabled channels = (even number < input buffer
size)
For other parallel port
instruments, if your sample rate is less than the bandwidth (or maximum
throughput) of your particular parallel port (i.e., 40,000 samples/second
for standard ports, 80,000 samples/second for bidirectional ports, and
250,000 samples/second for EPP), you can acquire pre- and post-trigger
data points based on the following formula:
(pre-trigger points + post-trigger points) × number of
enabled channels ≤ 64000
For other parallel port
instruments, if your sample rate is greater than the bandwidth (or maximum
throughput) of your particular parallel port (i.e., 40,000 samples/second
for standard ports, 80,000 samples/second for bidirectional ports, and
250,000 samples/second for EPP), the total number of pre- and post-trigger
data points times the number of enabled channels must be an even number
less than 7500.
(pre-trigger points + post-trigger
points) × number of enabled channels = (even number < 7500)
