1. Introduction
NI SC Express signal conditioning systems are composed of five basic components:
Figure 1. PXI measurement system comprised of chassis, controller, SC Express modules, and other peripheral modules.
2. PXI Express Chassis
The backplane of the PXI Express chassis provides a foundation for communication between NI PXI Express embedded controllers, SC Express modules, NI Modular Instruments and multifunction data acquisition (DAQ) modules. NI PXI Express chassis include all features of the latest PXI specification, accepting both PXI and PXI Express modules. The chassis feature a built-in 10 MHz reference clock, PXI trigger bus, and PXI star trigger for PXI modules as well as a built-in 100 MHz reference clock, SYNC 100, and PXI differential star trigger for PXI Express modules. With up to 24 GB/s total system bandwidth, these high-performance chassis offer enhanced manipulation of measurement data, and deliver high-throughput application needs. PXI Express chassis are available in a variety of sizes from 4-slot to 18-slot and with both 3U and 6U slot sizes available.
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Figure 2. Standard chassis options include the low-cost NI PXIe-1071 with an integrated controller (left), and the NI PXIe-1075 (right), which has 18 slots for the system controller and peripheral modules.
3. PXI Express Controllers
Most PXI chassis contain a system controller slot in the leftmost slot of the chassis. You can choose from a few options when determining the best system controller for an application, including remote controllers from a desktop, workstation, server, or laptop computer and high-performance embedded controllers with either a Microsoft OS or a real-time OS. The two types of remote controller options are via the express card bus or PCI Express bus.
PXI Embedded Controllers
Embedded controllers eliminate the need for an external PC, therefore providing a complete system contained within the PXI chassis. These embedded controllers come with standard features such as an integrated CPU, hard drive, RAM, Ethernet, video, keyboard/mouse, serial, USB, and other peripherals, as well as Microsoft Windows and all device drivers already installed. They are available for systems based on PXI or PXI Express, and you have your choice of OSs, including Windows 7/10 or NI LabVIEW Real-Time.
Figure 3. The NI PXIe-8880 controller has a 2.3 GHz eight-core Intel Xeon E5-2618L v3 processor.
PXI embedded controllers are typically built using standard PC components in a small, PXI package. For example, the NI PXIe-8880 controller has a 2.3 GHz eight-core Intel Xeon E5-2618L v3 processor (3.4 GHz maximum single-core, Turbo Boost mode), up to 8 GB of DDR3 RAM, the option of hard-disk drive or solid-state drive, and standard PC peripherals such as Hi-Speed USB, Ethernet, serial, and parallel ports.
PXI Remote Controllers
With NI ExpressCard MXI (Measurement eXtensions for Instrumentation) you can control PXI systems directly from laptop computers through a software-transparent link. During startup, the laptop computer recognizes all peripheral modules in the PXI system as PCI boards, and you can then control these devices through the laptop computer.
With an NI PCIe MXI card any PC with an available PCIe slot can control the PXI system directly. Like in the ExpressCard case the implementation will be software transparent. At startup the PC will detect the PXI peripherials and show them on the PCIe bus.
Some PXI chassis come with an integrated MXI controller built in allowing for all slots to be used on measurement modules. any PXI chassis though can be controlled via MXI by placing an NI PXIe MXI device in the first slot instead of an embedded controller.
Figure 4. Remote control with two-port MXI-Express provides simultaneous control of two PXI chassis with combined 160 MB/s throughput.
4. SC Express Modules
The SC Express family of high-performance PXI Express modules measure strain gages, bridge-based transducers, high-voltage analog input, thermocouples, dynamic voltages, microphones, accelerometers and fiber bragg optical sensors.
| SC Express Module | Connectivity Needs |
| NI PXIe-4300 Isolated Analog Input | NI TB-4300 (10V) |
| NI PXIe-4300 Isolated Analog Input | NI TB-4300B (300V) |
| NI PXIe-4300 Isolated Analog Input | NI TB-4300C (20mA) |
| NI PXIe-4302 32-Ch Analog Input (5 kS/s/ch) | NI TB-4302 (10V) |
| NI PXIe-4302 32-Ch Analog Input (5 kS/s/ch) | NI TB-4302C (20mA) |
| NI PXIe-4303 32-Ch Analog Input (51.2 kS/s/ch) | NI TB-4302 (10V) |
| NI PXIe-4303 32-Ch Analog Input (51.2 kS/s/ch) | NI TB-4302C (20mA) |
| NI PXIe-4304 32-Ch Analog Input (5kS/s/ch) | NI TB-4304 (42V) |
| NI PXIe-4305 32-Ch Analog Input (51.2kS/s/ch) | NI TB-4304 (42V) |
| NI PXIe-4309 32-Ch Flexible Resolution Analog Input | NI TB-4309(MT) for VHDCI connectivity |
| NI PXIe-4309 32-Ch Flexible Resolution Analog Input | NI TB-4309(ST) for screw terminal connectivity |
| NI PXIe-4310 Isolated Analog Input | NI TB-4310(10V) |
| NI PXIe-4310 Isolated Analog Input | NI TB-4310(600V) |
| NI PXIe-4330 Bridge Input (25 kS/s/ch) | NI TB-4330 |
| NI PXIe-4331 Bridge Input (102.4 kS/s/ch) | NI TB-4330 |
| NI PXIe-4339 Bridge and Voltage Input | NI TB-4339 (120 ohm) |
| NI PXIe-4339 Bridge and Voltage Input | NI TB-4339 (350 ohm) |
| NI PXIe-4339 Bridge and Voltage Input | NI TB-4339C (1000 ohm) |
| NI PXIe-4340 AC LVDT Input | NI TB-4340 |
| NI PXIe-4353 Thermocouple Input | NI TB-4353 |
| NI PXIe-4357 RTD Input | NI TB-4357 |
| NI PXIe-4322 Isolated Analog Output | NI TB-4322 |
| NI PXIe-4499 Dynamic Signal (4 Gains) | Infiniband cable |
| NI PXIe-4497 Dynamic Signal (2 Gains) | Infiniband cable |
| NI PXIe-4492 Dynamic Signal (2 Gains) | Infiniband cable |
| NI PXIe 4484 Optical Sensor (FBG) | None |
Table 1. Each SC Express module has its own compatible terminal block.
5. Smart Terminal Blocks
Front-mounting terminal blocks with screw terminal connectivity offer a simplified path to taking measurements. These devices are keyed to match with the appropriate SC Express modules and include alignment fins that guide the connector onto the PXI Express modules, preventing bent pins. The terminal blocks are hot swappable and automatically recognized in software, which adds to productivity by decreasing setup and troubleshooting time.
Figure 5. SC Express front-mounting terminal blocks are designed with screw terminals to directly connect signals and sensors.
6. Adding Peripheral Modules
Wide Variety of I/O on PXI Platform
With more than 1,500 products, the PXI platform provides flexible user-defined systems for automating measurements and making data available for analysis. As part of the PXI platform, the SC Express modules tightly synchronize with many PXI instruments. National Instruments offers more than 200 different PXI modules and because PXI is an open industry standard, more than 1,500 modules are available from more than 70 vendors. PXI modules for instrumentation at National instruments offer data acquisition, switching, motion, vision, advanced synchronization, and interfacing with other buses; allowing flexibility in creating a wide range of PXI systems. PXI modules commonly used in SC Express measurement systems include X Series, DAQ, and Timing and Synchronization modules
Figure 6. NI timing and Synchronization Modules Guarantee synchronization no matter how many channels
7. Software Architecture
NI-DAQmx driver software provides control for the PXI Express chassis, SC Express modules, and a wide range of data acquisition and signal conditioning devices. Along with LabVIEW, NI-DAQmx is also compatible with NI SignalExpress, NI LabWindows™/CVI, C/C++, Visual Basic, Visual Basic .NET, and C#. The NI-DAQmx driver is shipped with every DAQ device compatible with NI-DAQmx, and is also available for download from ni.com.
Figure 7. NI-DAQmx provides the connection from SC Express HW to various SW development
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