32
Operation Theory
data should be transferred into PC’s memory for further
processing. PCI-9812/10 uses DMA to transfer the A/D data to
host memory. Please refer to section 5.5.
To process A/D data, programmers should be familiar with the A/D
data format. Please refer to section 5.6.
5.2 A/D Signal Source Control
To control the A/D signal source, the following three concepts
should be understood: signal type, signal channel, and signal
range.
Signal Type
The A/D signal sources of PCI-9812/10 are single ended (SE).
Numbers of Channel
There are four channels for SE mode. The ADC Channel Enable
Register controls the channel number. Please refer to section 4.2.
Signal Range and Input impedance
The proper signal range is important for data acquisition. The
available signal input ranges for 9812/10 are
±
5V or
±
1V, which
are set by soldering the copper pads on the PCB. The input
impedance for high-speed applications should also be considered.
The selectable input impedance values are 50 Ohm, 1.25K, 15M
ohm. Please refer to section 3.2 for details.
5.3 A/D Trigger Source Control
Performing the trigger acquisition in PCI-9812/10, the following
items have to be specified before DMA operation starts:
Clock source:
refer to section 5.4
Clock rate:
refer to section 5.4
Trigger source:
refer to section 5.3
Trigger level:
The trigger event occurs when the trigger signal
crosses the specified trigger voltage. Please refer to section 4.5
Summary of Contents for NuDAQ PCI-9810
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