Ultimate test

Data collection and analysis has reached new levels with software capable of turning a personal computer into a powerful measurement tool. Charles Clarke reports

From as far back as the time of ancient Greeks and Mayans, operators have looked at scientific instruments and written down observations.

It was not until the arrival of the computer that data could be acquired and stored automatically. The introduction of the digital computer provided the platform to not only acquire and store data but also analyse and report it.

This is achieved using a three-part data acquisition (DAQ) system that consists of an input/output sub-system, a PC and the controlling software.

Today a wide variety of firms make data acquisition and control interfaces for the PC. Most systems have an internal plug-in board configuration or an external box.

The majority of plug-in board business is based on the PCI bus (or variants such as cPCI and PXI) and is starting to follow the lead of the consumer PC vendors into PCI Express.

The external box vendors now have Ethernet and USB standards to work with as well as some less used, but viable, interfaces such as Firewire, CAN, and perhaps the oldest standard in computing, RS-232.

Combined with advanced software, these DAQ input/output systems will turn a personal computer into a useful measurement tool. Software such as MATLAB and LabVIEW are designed to make the most of extremely powerful applications and are easy to use.

How a user sets up their data acquisition system is highly dependent on the application. However, many people are finding that the availability of USB 2.0 is changing the industry as much as the introduction of the IBM PC did in the 1980s. It frees everyone from having special DAQ boards and special connectors.

Imagine the problems associated with data collection when testing high performance passenger cars.

The vehicle is moving at 160mph on a test track or over distressed road surfaces. The components under test will be subject to multiple g forces and vibrations.

How would you design such a system? How could you ensure the test equipment and computer capturing the data would not fail under these harsh conditions? Finally, how would you do all this at significant savings, reducing the cost of the test system by up to 30 per cent?

A large automotive component manufacturer that supplies equipment to major car manufacturers formed a partnership with Data Translation to design a solution.

To acquire the data in a moving vehicle during the test drives, they used an industrial notebook computer running Windows XP. Hard drive failure was a real concern in this scenario. To avoid hard disk problems, the data is saved in flash memory on a USB 2.0 memory stick, and the disk is switched off during measurement.

Although USB is commonly thought of as a peripheral bus for keyboards, mice, and similar low-demand devices, USB 2.0 provides the required high data throughput, at 40 MB/sec, for rapid data storage. With the addition of a battery backup, the manufacturer has a robust, lightweight computing platform that came in 30 per cent below competitive offerings.

The design, and especially the operational reliability, of bathroom fittings or shower heads is just as critical. These components must run smoothly even if the water supply is sometimes irregular. Abrupt changes in temperature or pressure in the cold and hot water supply is a serious disturbance to the user’s comfort and wellbeing. This makes it all the more important to run extensive and precise quality tests.

One company, measX, has equipped such a test stand for Hansgrohe, in Georgia, US, with the software and the necessary measurement boards. The measurement system provides extensive, standardised and user-friendly test programs that the user can adapt to the respective test object and use to run individual tests.

The software has a diagnosis mode that can carry out a function check and search for errors.

The measurement software was developed alongside the DASylab software from National Instruments(available through Adept Scientific) that is used for data acquisition, data control, data analysis and data presentation.

Because of the graphical interfaces in DASylab, the user does not need programming skills to run quality control tests.

MathWorks’ MATLAB is another industry standard DAQ and analysis package, and the company’s Data Acquisition Toolbox allows users to read data directly into MATLAB and Simulink environments from selected hardware boards for immediate analysis.

Data Acquisition Toolbox software provides a complete set of tools for analogue input, analogue output and digital input/output from a variety of PC-compatible data acquisition hardware.

MATLAB provides support for multiple hardware manufacturers. It offers flexibility to help users mix hardware from multiple manufacturers when creating MATLAB applications. This means they can switch data acquisition hardware in the future while continuing to use MATLAB as their software environment.

Other MathWorks products provide additional options for communicating with external hardware devices from within MATLAB.

MATLAB supports instruments and hardware that use GPIB (IEEE-488, HPIB), VISA, TCP/IP, UDP, and serial standards through the Instrument Control Toolbox.

To communicate with cameras and frame grabbers, MathWorks offers an ‘image acquisition toolbox’.

For real-time closed-loop control applications, the company offers products based on Simulink, such as xPC Target and Real-Time Windows Target.

In our CAD Software feature, which appeared in the 1 September issue of Design Engineering, we referred to PTC Software of Cambridgeshire. This should, of course, have read PTC, the global enterprise software group.