Thursday 27 May 2010

Integrated signal conditioning for scalable, high-performance measurements

Strain, thermocouple and high-voltage analogue input modules offer increased accuracy for high-channel-count measurement systemsNational Instruments has announced the company’s first data acquisition (DAQ) modules with integrated signal conditioning for scalable, high-performance measurements on PXI Express. The new NI SC Express family delivers increased accuracy, high data throughput and best-in-class synchronisation for measuring strain gauges, bridge-based transducers, thermocouples and high-voltage analogue inputs. PXI Express provides 250 MB/s of dedicated bandwidth for each SC Express module in the chassis, which helps engineers increase channel count without compromising sampling rates or data throughput. With a smaller footprint, simplified cable management and new software features for automatic synchronisation, the SC Express modules make it easy for engineers to set up and program high-channel-count sensor measurement systems.

The PXIe-4330 24-bit simultaneous bridge input module offers 0.02 percent accuracy and 25 kS/s per channel sample rate for high-performance strain, load, force and torque measurements. The bridge input module achieves high accuracy with a ratiometric design where the ADC references the excitation voltage. This approach removes the measurement’s dependence on the stability and accuracy of the excitation voltage. In addition, unique delta-sigma ADCs provide both excellent AC performance as well as DC accuracy, while traditional delta-sigma ADCs only offer AC performance.

This bridge input module can perform quarter, half and full bridge-based measurements with automatic synchronisation features. The included driver software ensures tight synchronisation across multiple modules and chassis with inter-channel skews as low as 5 ppb. The 8-channel bridge input module can scale to a 136-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The high-accuracy, simultaneity and synchronisation features make the NI PXIe-4330 module ideal for high-channel-count structural test applications, such as wind tunnels, bridge monitoring and crash tests.

With the thermocouple module, engineers can measure temperatures with 0.30 °C accuracy on 32 channels. The isothermal terminal block minimises error with a unique design that optimises thermal conductivity, making it possible for the nearby cold-junction compensation (CJC) thermistors to accurately measure at the thermocouple junctions. The 32-channel thermocouple module can scale to a 544-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The increased accuracy and scalable platform make the NI PXIe-4353 module well-suited for precision measurements from a single channel to large systems for applications such as fuel cell testing and monitoring thermal chambers.

The high-voltage isolated analogue input module is the first analogue input module from National Instruments that can measure up to 300 V with simultaneous sampling. With a 16-bit ADC per channel and a 250 kS/s per channel sampling rate, the NI PXIe-4300 module can stream 4 MB/s per module and 68 MB/s in a single chassis. This 8-channel analogue input module can scale to a 136-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The ability to measure 300 V with CAT II channel-to-channel isolation makes the NI PXIe-4300 module ideal for automotive testing, such as fuel cell and battery tests.

The new SC Express modules include NI-DAQmx driver software and support for multi-device tasks, a new feature of NI-DAQmx that helps engineers easily synchronise multiple modules. The same code that acquires data from one module can synchronise up to 17 modules in a chassis. The modules work with a variety of NI hardware including NI X Series, dynamic signal acquisition (DSA) and NI SCXI products, and more than 1,500 types of I/O available on the PXI platform. The new modules also integrate with NI software including NI LabVIEW and the LabVIEW Real-Time Module, NI-Sync and NI DIAdem.

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