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NI 6520/6521 User Guide
6
ni.com
Related Documentation
The following documents contain information that you may find helpful as
you use this user guide:
•
DAQ Getting Started Guide
—This guide describes how to install the
NI-DAQ software, the DAQ device, and how to confirm that the device
is operating properly.
•
NI-DAQmx Help
—This help file contains information about using
NI-DAQmx to program National Instruments devices. NI-DAQmx
is the software you use to communicate with and control NI DAQ
devices.
•
Measurement & Automation Explorer Help for NI-DAQmx
—This
help file contains information about configuring and testing DAQ
devices using Measurement & Automation Explorer (MAX) for
NI-DAQmx, and information about special considerations for
operating systems.
•
DAQ Assistant Help
—This help file contains information about
creating and configuring channels, tasks, and scales using the DAQ
Assistant.
Note
You can download these documents from
ni.com/manuals
.
Features
Digital Filtering
Use the digital filter option available on the NI 6520/6521 input lines to
eliminate glitches on input data. When used with change detection, filtering
can also reduce the number of changes to examine and process.
You can configure the digital input channels to pass through a digital filter
after the photocouplers, and you can control the timing interval the filter
uses. The filter blocks pulses that are shorter than half of the specified
timing interval and passes pulses that are longer than the specified interval.
Intermediate-length pulses—pulses longer than half of the interval but less
than the interval—may or may not pass the filter.
The filter operates on the inputs from the photocouplers. Photocouplers
turn on faster than they turn off and pass rising edges faster than falling
edges. As a result, the photocouplers can add up to 100
μ
s to a high pulse
or subtract up to 100
μ
s from a low pulse.
Note
A 100
μ
s change is typical when I
F
= 16 mA, and R
L
= 10 k
Ω
.