Description

NI PXI-4351 | High-Precision Temperature & Voltage Meter | PXI Data Acquisition

Key Technical Specifications

NI documentation confirms that the PXI-4351 uses a 24-bit sigma-delta ADC with differential analog inputs and supports thermocouples, RTDs, thermistors, resistance, and current measurements. Its integrated precision current sources include a 25 µA source with a 600 kΩ maximum load and a 1 mA source with a 15 kΩ maximum load.

Product Introduction

The NI PXI-4351 is a precision measurement module from the National Instruments NI 435x family, designed primarily for temperature and low-frequency voltage acquisition in PXI-based test and measurement systems. Its 24-bit sigma-delta converter and differential measurement architecture allow it to handle thermocouple, RTD, thermistor, resistance, and voltage measurements without treating the module as a conventional high-speed multifunction DAQ card.

The NI PXI-4351 also includes programmable TTL-compatible digital I/O and onboard precision current excitation for resistance-based sensors. It can be installed in an available 5 V PXI peripheral slot or a compatible CompactPCI chassis arrangement. For legacy production-test equipment, semiconductor test stations, environmental measurement systems, and laboratory instrumentation, preserving the original software environment can be just as important as obtaining the correct hardware.

PXI-4351

Application Scenarios & Field Pitfalls — The Engineer’s Perspective

Engineering Pain Point

With the PXI-4351, the main replacement risk is often software compatibility rather than electrical compatibility. The hardware may physically install into a PXI chassis, but the NI-435x driver architecture is old. NI documentation classifies the PXI-4351 as a Traditional NI-DAQ legacy device, and an NI support response specifically stated that the device was obsolete and supported only Windows XP 32-bit in that historical support context.

Typical Applications

Temperature measurement systems
The PXI-4351 is designed for accurate thermocouple, RTD, and thermistor acquisition and can serve as the measurement front end in automated temperature logging equipment.

Semiconductor and manufacturing test
Its combination of temperature measurement, precision voltage measurement, resistance measurement, and programmable digital I/O makes it suitable for older automated test systems.

Environmental monitoring
Thermocouple and resistance-based sensors can be connected for low-frequency temperature monitoring and data logging.

Laboratory instrumentation
The PXI architecture allows the measurement module to operate alongside other PXI instruments under a centralized test application.

Technical Pitfalls

1. Do not treat PXI-4351 as a modern DAQmx device.
   NI identifies the PXI-4351 as a Traditional NI-DAQ (Legacy) device. Its software environment needs to be checked before replacing hardware.
2. PXI and PXIe are not interchangeable assumptions.
   The PXI-4351 is an older PXI-generation module. Do not assume that replacing it with a PXIe instrument provides drop-in hardware and software compatibility. NI specifically noted that the later PXIe-4353 used a different timing architecture and was not designed as a PXI-form-factor replacement.
3. Check the operating system before purchasing.
   Historical NI support information states that the PXI-4351 was limited to Windows XP 32-bit support. For a legacy test station, the existing controller image, driver version, LabVIEW version, and application dependencies should be documented before changing the module.
4. Do not confuse channel count with simultaneous measurement.
   The PXI-4351 is intended for high-precision, relatively low-frequency measurement. It is not a high-speed oscilloscope or high-bandwidth multifunction DAQ module.
5. Sensor wiring affects resistance accuracy.
   When using the onboard current sources for RTDs, thermistors, or resistance measurements, resistance in the sensor leads contributes measurement error. NI documentation explicitly notes this effect.
6. Cold-junction compensation matters for thermocouples.
   Thermocouple measurements depend on the terminal/connection temperature and the applicable accessory configuration. The terminal block and sensor wiring should therefore be treated as part of the measurement chain rather than as simple passive wiring.
7. Check the complete part number.
   777790-01 is associated with the PXI-4351. Other 435x-family hardware, including the PCI-4351, has a similar measurement function but uses a different bus and physical implementation.
8. Do not confuse the PXI-4351 with the PCI-4351.
   Both belong to the NI 4351 measurement family, but PXI and PCI installations require different host interfaces and system configurations.

Related Products

• NI PCI-4351 — PCI version of the 4351 temperature/voltage measurement platform; not a direct PXI hardware substitute.
• NI USB-4350 — USB member of the NI 435x family, using the same general measurement architecture but a different host interface.
• NI PXIe-4353 — Later PXIe temperature measurement platform recommended by NI as a modernization path, but not a drop-in PXI replacement for the PXI-4351.
• NI PXI-1042 — Example PXI chassis used with PXI-4351 installations; chassis compatibility should be verified for the complete test system.
• NI PXI-8360 / PCIe-8361 — PXI controller/interface hardware seen in legacy PXI systems; compatibility depends on the host architecture.
• NI 435x Driver — Legacy instrument driver required for PXI-4351 software operation.
• VI Logger — Historical NI data-logging software used with NI 435x hardware.
• NI PXI temperature measurement modules — Later-generation alternatives may use DAQmx and PXIe, requiring application migration rather than simple card replacement.

Procurement Note

For purchasing and maintenance records, specify:

National Instruments PXI-4351 — P/N 777790-01 — NI 435x High-Precision Temperature and Voltage Measurement Module

For a legacy installation, collect the PXI chassis model, controller/PC model, operating system, NI-435x driver version, LabVIEW version, VI Logger usage, terminal block/accessory model, sensor types, and existing application files before approving a replacement.

For used or surplus inventory, test the module in an appropriate PXI chassis and verify more than basic device enumeration. A meaningful acceptance test should include representative thermocouple or resistance measurements, voltage acquisition, digital I/O operation where used, and communication with the existing NI-435x software environment.

Engineering classification: NI PXI-4351 = legacy high-precision temperature and voltage measurement module with 24-bit sigma-delta ADC, 16 differential voltage inputs / 14 thermocouple inputs, and 8 TTL-compatible digital I/O lines. It is a test-and-measurement instrument rather than a PLC/DCS I/O module.