Chapter 3
Hardware Overview
PCI-4451/4452/4453/4454 User Manual
3-4
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Analog Input
The analog input section of each PCI-445X is software configurable. You
can select different analog input configurations through application
software. The following sections describe in detail each of the analog input
categories.
Input Mode
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PCI-4451/4452
This device has differential (DIFF) inputs. You can configure the input as a
differential or a single ended (SE) channel using the BNC-2140 DSA
accessory. For more information, please refer to the BNC-2140 User
Manual. In DIFF mode, one line connects to the positive input of the
channel, and the other connects to the negative input of the same channel.
You can connect the differential input to SE or DIFF signals, either floating
or ground-referenced. However, grounding the negative input from floating
sources can improve the measurement quality by removing the
common-mode noise.
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PCI-4453/4454
This device operates in SE mode using the BNC-2142 DSA accessory.
For more information, refer to the BNC-2142 Installation Guide.
Input Coupling
The PCI-445X has a software-programmable switch that determines if a
capacitor is placed in the signal path. If the switch is set for DC, the
capacitor is bypassed, and any DC offset present in the source signal is
passed to the ADC. If the source has a significant amount of unwanted
offset (bias voltage), you must set the switch for AC coupling to place the
capacitor in the signal path and take full advantage of the input signal
range.
Input Polarity and Input Range
The PCI-445X operates in bipolar mode. Bipolar input means that the input
voltage range is between –V
ref
/2 and +V
ref
/2.
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PCI-4451/4452
This device allows you to configure the range settings of each input channel
independently. The software-programmable gain on this device increases
