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Chapter 4
Analog Input
Table 4-6 shows the input ranges and resolutions supported by the Simultaneous MIO X Series
device family.
Working Voltage Range
On most Simultaneous MIO X Series devices, the PGIA operates normally by amplifying
signals of interest while rejecting common-mode signals under the following three conditions:
•
The common-mode voltage (Vcm), which is equivalent to subtracting AI <0..
x
> GND from
AI <0..
x
>-, must be less than ±10 V. This Vcm is a constant for all range selections.
•
The signal voltage (Vs), which is equivalent to subtracting AI <0..
x
>+ from AI <0..
x
>-,
must be less than or equal to the range selection of the given channel. If Vs is greater than
the range selected, the signal clips and information are lost.
•
The total working voltage of the positive input, which is equivalent to (Vcm + Vs), or
subtracting AI <0..
x
> GND from AI <0..
x
>+, must be less than ±11 V. This does not apply
to the NI 6346 and NI 6349, which have lower working voltages for lower ranges. Refer to
the device specifications on
ni.com/manuals
for working voltage values per range.
If any of these conditions are exceeded, the input voltage is clamped until the fault condition is
removed.
Analog Input Data Acquisition Methods
When performing analog input measurements, you either can perform software-timed or
hardware-timed acquisitions.
•
Software-timed acquisitions
—With a software-timed acquisition, software controls the
rate of the acquisition. Software sends a separate command to the hardware to initiate each
ADC conversion. In NI-DAQmx, software-timed acquisitions are referred to as having
on-demand timing. Software-timed acquisitions are also referred to as immediate or static
acquisitions and are typically used for reading a single sample of data.
•
Hardware-timed acquisitions
—With hardware-timed acquisitions, a digital hardware
signal (AI Sample Clock) controls the rate of the acquisition. This signal can be generated
internally on your device or provided externally.
Table 4-6.
Simultaneous MIO X Series Device Input Range and Nominal Resolution
Simultaneous MIO
X Series Device
Input Range
Nominal Resolution Assuming
5% Over Range
NI 6346/6349/6356/6358/
6366/6368/6374/
6376/6378/6386/6396
-10 V to 10 V
320
μ
V
-5 V to 5 V
160
μ
V
-2 V to 2 V
64
μ
V
-1 V to 1 V
32
μ
V
Summary of Contents for 6368
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