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COTS Components Become Application-Specific, Total Data Acquisition Solutions

Wed, 05/25/2011 - 7:57am
Jeff Elliott, Technical Writer, KineticSystems
By definition, the off-the-shelf modular instruments (VME, PXI, VXI, CompactPCI, PCI, etc.) used to create automated test and measurement systems are designed to be general purpose, programmable, and flexible enough to handle a variety of input ranges and types, speeds, and functions.

At first blush, these modular off-the-shelf instruments may seem ready-to-go for instrument manufacturers or test system designers’ needs. However, 100 percent COTS are generally inadequate for complex, commercialized measurement systems. Often these instruments, built into systems within a chassis or PC, are utilized in a laboratory or R & D environment, with techniques or information that was not previously available.

“Flexibility is built into these types of cards so they can deal with multiple conditions,” says Steve Krebs, of KineticSystems, a company that offers CompactPCI/PXI and VXI data acquisition (DAQ) modules for test and measurement applications. “Manufacturers cannot anticipate everything, particularly in cutting edge applications, so customization still enters into the equation.”

Figure 1. By definition, off the shelf modular instruments used to create automated test and measurement systems are designed to be general purpose, programmable and flexible. However, to meet the neeAlthough most of an instrument manufacturer’s revenue comes from off-the-shelf module sales, customers are increasingly requiring some level of hardware, software or firmware modifications to fit the application.

Although some customization can be handled by the customer’s engineering staff, modifications are a time-consuming and expensive activity that consume resources and detract from a company’s core activity.

As a result, it behooves manufacturers to partner with instrument providers willing to semi-customize COTS products. Unfortunately, high volume manufacturers are often only interested in providing off-the-shelf products and are ill equipped or unwilling to provide semi-customized products.

Fortunately, smaller instrument manufacturers are typically more willing – often free of charge or at nominal cost – to provide semi-custom solutions along with its portfolio of off-the-shelf products.

Recently, a PXI system project was completed for an automotive component testing application, in this case for testing automotive accelerator pedals. The testing involved temperature controlled test chambers to simulate worst case environments. The pedals are mechanically cycled continuously for months while the system records the position and monitors the motion profile to ensure the pedal is performing as designed. In some instances, stress is also measured.

The original ATE system developed for this purpose was a proprietary non-standards based system no longer supported by its manufacturer. Later, the system was updated with VXI components, but was still largely proprietary.

The requirements for a standardized solution that could easily be duplicated were satisfied using four modular off-the-shelf eight-channel CompactPCI/PXI modules with signal conditioning and ADC in a rack mounted enclosure.

Figure 2. Complex, commercialized test and measurement systems often require more than an assemblage of modular, off-the-shelf cards. The system shown here includes instruments from KineticSystems andThe customer also wanted to perform more frequent calibration of the instruments in its own metrology labs. Typically, calibration is performed annually at the manufacturer’s facility. However, calibrating in house would minimize downtime and expense. In response, KineticSystems developed a standalone software application to perform periodic calibration with report generation for NIST traceability.

The customer also required the ATE to have the built-in flexibility to perform ad-hoc data acquisition experimentation without having to write any code. This was achieved through configurable data acquisition software that provides access to all of an instrument’s features through a simple point and click GUI.

In another semi-customization example, the purchase of a COTS digitizer module allowed a U.S. manufacturer of laser instrument systems for specialized inspection at electrical and geological sites to reduce engineering costs and time-to-market while focusing on its core activity and not instrument manufacturing.

The manufacturer had been dedicating valuable resources to engineer a digitizer card in house. Although commercial digitizers were available at the time the product was initially created, FPGAs (field-programmable gate arrays) that perform on board signal processing on a COTS digitizer were not.

Later, when the product started to take off, the manufacturer decided to incorporate an off-the-shelf digitizer into its system. After some research, the customer selected a 12-bit solution from GaGe, a manufacturer that had just released one of the industries’ first high-speed PCI/PCIe digitizers with FPGA programmability.

Almost immediately, however, it was clear that the FPGA provided was still not large enough for the application. Fortunately, a larger, pin compatible FPGA was available and was added by the manufacturer without changing the circuit board, which would have entailed much higher costs.

The customer then realized belatedly that the digitizer they had developed in house was also equipped with low-speed A/D, D/A, IO to capture analog temperature measurements, activate motors, and turn the various devices on and off.

To add these elements, the digitizer manufacturer partnered with KineticSystems to deliver what became a two-board solution – the digitizer and a PXI DAQ data acquisition board from KineticSystems that was modified to operate from a USB port.

Next, the manufacturer needed to address a unique low-power requirement. Because the laser instruments were used to monitor conditions in remote locations with no ready access to power, the units utilized solar powered rechargeable batteries. This created a strict power budget.

“The board they selected had multiple input ranges and multiple channels and the customer only required one,” says Andrew Dawson of GaGe. “We removed a channel and the amplifiers, which resulted in a 50 percent reduction in the power required.”

Another element that had to be addressed was the duration of the trigger pulse used to activate the laser beam. Although adequate for most applications, the standard trigger pulse was too short, causing the laser to activate intermittently and therefore unreliably. Adding an external circuit would have solved the problem, but would add cost. Engineers modified the card to extend the trigger pulse duration.

“Although by itself each of these modifications might appear minor, the ensemble of modifications provided the customer with a complete, application-specific solution,” says Dawson. The bottom line is modular instrument manufacturers need to be able to deliver the best of both worlds: a level of customization at the price and timing of COTS products.

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