High-Precision Data Acquisition
NI PCI-4351, NI PXI-4351
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Temperature and voltage loggers
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Accuracy – 0.42 °C for J-type
thermocouples, 0.03 °C for
thermistors, 0.12 °C for RTDs
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16 voltage or 12 thermocouple
inputs; up to 60 readings/s
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8 digital I/O lines (TTL)
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Autozero and cold-junction
compensation
Operating Systems
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Windows XP/2000/NT
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LabVIEW Real-Time
Recommended Software
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LabVIEW
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LabWindows
™
/CVI
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Measurement Studio
Driver Software (included)
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NI-435x instrument driver
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Traditional NI-DAQ (Legacy)
Family
NI 4351
Bus
PCI, PXI
Voltage/
(Thermocouple)
Channels
16/(14)
RTD
Accuracy
(°C)
0.12
Thermistor
Accuracy
(°C)
0.03
reject 50, 60, and 400 Hz noise, based on the reading rate. The input circuitry
Resistance
Measurement
Excellent
delivers ±42 V overvoltage protection and per-channel lowpass, antialiasing
filters. An NI 4351 device features software-selectable ground referencing
on a channel-by-channel basis, so you can measure both floating and ground-
referenced signals together; it also features per-channel open-thermocouple
detection. When open-thermocouple detection is enabled, the input channel is
connected to +2.5 VDC through a 10 MΩ resistor. When a thermocouple breaks
or is disconnected, the reading rapidly increases to 100 mV or more, indicating
an open-circuit condition.
Table 1. High-Precision DAQ Selection Guide
Overview
The NI PCI-4351 and PXI-4351 are precision computer-based digitizers designed
specifically for high-accuracy temperature measurements (thermocouples,
RTDs, thermistors), resistance measurements, chromatography measurements,
and low-frequency analog signal measurements within ±15 V. Available for
PCI and PXI/CompactPCI, these devices feature ±0.42 °C, J-type thermocouple
accuracy; ±0.12 °C RTD accuracy; ±0.03 °C thermistor accuracy; 5�½-digit voltage
measurements; power line noise rejection filters; and precision current source
for RTD and thermistor excitation. NI 4351 devices combine the functionality
of stand-alone temperature and voltage meters and chromatographs with
the flexibility and benefits of your computer, so you can build highly capable
computer-based data-logging systems. As with all computer-based digitizers,
NI 4351 devices can easily integrate into your Internet-based applications.
Precision Current Excitation
These devices feature a 25 μA precision current source for excitation
of RTDs, thermistors, or other resistive devices. The source excites the total
system resistance of up to 600 kΩ. An NI 4351 also features an additional
1 mA precision current source for RTDs or other resistive devices for total system
resistance of up to 15 kΩ.
Digital I/O and Alarm Outputs
An NI 4351 has eight 5 V/TTL digital lines. You can individually configure each
line as an input or an output. You can use the lines as general-purpose digital I/O
or as control lines for alarms. Each line sinks or sources 8 mA. With the TBX-68T
or CB-68T, you can increase the sinking and sourcing capability of these digital
lines to 64 and 15 mA, respectively. With digital signal conditioning accessories,
such as the ER-8, SSR Series, and the SC-206x, you can use an NI 4351 to
control relays and drive optically isolated digital I/O.
Hardware
Precision Analog Input
NI 4351 devices have 16 differential analog inputs. Each device has a 24-bit
analog-to-digital converter (ADC) and six possible reading rates – 10, 50, and
60 readings/s in single-channel acquisition mode and 2.8, 8.8, and 9.7 total
readings/s in multiple-channel acquisition mode. For channel speed, divide the
total readings/s by the number of channels acquired. Digital filters automatically
NI [ NATIONAL INSTRUMENTS CORPORATION ]
