National Instruments PCI-1200 用户手册

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repeat this process every 65 ms, then you should define the operation as 
follows:

•

Start channel:

ch1 (which gives a scan sequence of “ch1, ch0”)

•

Sample interval:

12

µs 

•

Scan interval:

65 ms

The first channel will not be sampled until one sample interval from the 
scan interval pulse. Since the A/D conversion time is 10

µs, your sample 

interval must be at least this value to ensure proper operation.

The PCI-1200 executes a single-channel analog input operation by 
performing an A/D conversion on a specified analog input channel every 
sample interval. The sample interval is the amount of time that elapses 
between successive A/D conversions. The sample interval is controlled 
either externally by EXTCONV* or internally by counter A0 of the timing 
circuitry.

To specify a single-channel analog input operation, select an analog input 
channel and a gain setting for that channel.

The PCI-1200 executes a multichannel DAQ operation by repeatedly 
scanning a sequence of analog input channels (the same gain is applied to 
each channel in the sequence). The channels are scanned in decreasing 
consecutive order; the highest-numbered channel is the start channel, and 
channel 0 is the last channel in the sequence.

During each scan sequence, the PCI-1200 scans the start channel (the 
highest-numbered channel) first, then the next highest-numbered channel, 
and so on until it scans channel 0. The PCI-1200 repeats these scan 
sequences until the DAQ operation is terminated.

For example, if channel 3 is specified as the start channel, then the scan 
sequence is as follows:

ch3, ch2, ch1, ch0, ch3, ch2, ch1, ch0, ch3, ch2, …

To specify the scan sequence for a multichannel scanned analog input 
operation, select the start channel for the scan sequence.