Chapter 4 Analog Input Reference
Measure Data Acquisition User Manual
4-4
© National Instruments Corporation
Low Limit
Enter the lower voltage limit for the channels in the channel string.
This voltage is the minimum voltage that is measured at any of the
analog input channels that are specified in the channel string. You may
add more than one channel string to your scan list and each channel
string may have a different set of high and low limits. When you create
an AI task, Measure enters the default value for your device.
Note:
Not all devices can have scan lists in which different channels can have
different high and low limit settings.
Scan Information
The following options apply to all the channels in the scan list.
Number of scans
Specify the number of scans for the acquisition. The number of scans is
the number of data acquisitions or readings to acquire from each
channel.
Scale to volts
Select this option if you want Measure to display the acquired data in
volts. Otherwise, Measure displays the data as the binary values read
from the analog-to-digital converter (ADC).
Timing Settings
You can think of a scan as a snapshot of the voltages present on your
channels at one time. The scan rate determines how many scans per
second Measure executes, which means that Measure samples each
channel at the scan rate you choose. If you set your scan rate to 10
scans per second, you are taking 10 snapshots each second of all the
channels in you scan list. If channel 2 is in your scan list, you sample
channel 2 ten times per second. You can think of your scan rate as your
sampling rate per channel.
In reality, your device does not take a snapshot of all your channels
instantaneously, unless it has the capability to do simultaneous
sampling. Rather, for each scan (as timed by the scan clock), the device
proceeds from one channel in the scan list to the next depending on the
channel clock rate. The faster the channel clock rate, the more closely
