Using LabVIEW and PXI to Detect Compressor Vibration Tester Defects

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"As a powerful graphical system design tool, LabVIEW plays a big role in reducing development time with its powerful analysis library, which removes all complexity in mathematics algorithm development. We finished our project incredibly quickly using this easy-to-use programming tool."

- Taradol Sirijuntakul, Sensornic Co., Ltd.

The Challenge:
Detecting all defect criteria that cannot be detected with an old single-axis vibration test system.

The Solution:
Utilizing powerful online PXI analysis and off-the-shelf simultaneously sampling hardware to detect all defect criteria by analyzing sound and vibration signals in all axes.

Author(s):
Taradol Sirijuntakul - Sensornic Co., Ltd.

Sensornic Co., Ltd. provides complete, high-quality measurement and automation solutions. Knowing our reputation as a National Instruments Alliance Partner, our customer tasked us with providing the solution to improve a compressor vibration tester that cannot detect certain defect criteria.

We selected NI for our solution because it offers a ready-to-use analysis library, powerful signal-processing hardware, and off-the-shelf simultaneously sampling hardware—critical in detecting hidden defect criteria. Additionally, the sound and vibration case studies on ni.com also significantly boosted our customer’s confidence in NI products.

System Capabilities and Benefits

The old system can only measure vibration in single-axis mode, and is unable to detect certain defect criteria. Our compressor test system measures sound level and axis vibration at different rotational speeds in online monitoring or defect-detection measurement mode, as shown in Figure 1.

The IEPE microphone attached in position “A” measures the sound waveform from 2 Hz to 200 kHz. The time waveform displays on the test system front panel with peak-to-peak sound level, damped value, and other sound measurements. The system also uses signal processing to remove background noise and increase measurement accuracy. At position “B”, a triaxis ICP acceleration sensor measures acceleration in multiple measurements, including overall vibration level and fast fourier transform.

This system utilizes a PC-based platform for test, measurement, and control. It also takes advantage of PXI ruggedness, high reliability, and high processing power. At the heart of the system is a PXI-4462 dynamic signal acquisition (DSA) module for acquiring both the microphone and accelerometer signals. Two important PXI-4462 characteristics that benefit this test system include:

  • A very high resolution at 24 bits. With this resolution, the system can detect a very small defect criteria signature.
  • An antialiasing filter, which helps remove unwanted frequency from the acquired signal.

On the software side, we used LabVIEW for developing both the measurement and analysis systems. With the LabVIEW ready-to-use analysis library, we can focus on the measurement system without reinventing the mathematics algorithm. Additionally, one of the systems must be running with a real-time OS, which would otherwise need a separate tool for programming. With the LabVIEW Real-Time Module, we used the same platform throughout the development cycle, without needing additional tools that waste time and money. LabVIEW also supports many other types of I/O necessary for the system, including a PXI-6515 with digital I/O that displays machine status. We can also easily expand the system in the future with open PXI slots.

As a powerful graphical system design tool, LabVIEW plays a big role in reducing development time with its powerful analysis library, which removes all complexity in mathematics algorithm development. We finished our project incredibly quickly using this easy-to-use programming tool. We also took advantage of NI professional support to help us troubleshoot challenges throughout the project.

In conclusion, with powerful PXI analysis and simultaneously sampling, off-the-shelf I/O, we could acquire and analyze sound and vibration signals in all axes in real time to detect hidden defect criteria.

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