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Customizing COTS Testing Systems
System shown here includes instruments from KineticSystems and highpspeed digitizers from GaGe, semi-customized to work as a complete system.
By Jeff Elliott
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 used to build systems that are utilized in a laboratory or R&D environment, with techniques or information that was not previously available.
"We build flexibility into our cards so they can deal with multiple conditions," says Steve Krebs, of KineticSystems, a company that offers a wide selection of CompactPCI/PXI and VXI data acquisition (DAQ) modules for test and measurement applications. "For instance, we have multiple input ranges on our cards. But we can't anticipate everything, particularly in cutting-edge applications, so that's where customization still enters into the equation."
Although nearly 90 percent of the company's revenue comes from off-the-shelf module sales, Krebs notes that an increasing number of customers require some level of hardware, software or firmware modifications to fit the application.
"With modular instruments, there is this idea that you can buy different pieces from Vendor A, B and C and stick them together in a system and that'll be it," says Krebs. "But once you put these modules together in a chassis, there can be issues with interoperability, input ranges, synchronization, signal amplitude or conditioning, and other performance characteristics."
Although some customization can be handled by the customer's engineering staff, modifications can be a time-consuming, 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, the high volume manufacturers are often only interested in providing off-the-shelf products and are ill-equipped or unwilling to provide semi-customized products.
According to Krebs, smaller instrument manufacturers such as KineticSystems 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.
PXI Testing Application
KineticSystems recently completed work for an automotive component testing application. The system was for an automotive component-level development and testing division of a large company that supplies products to many different industries.
The project involved an upgrade of the company's current data acquisition system for testing component-level assemblies for automobiles, in this case accelerator pedals. The customer required a COTS solution to replace existing instrumentation for lower cost and same performance as its existing system.
The testing process involved temperature-controlled test chambers to simulate the worst case component environments. The accelerator pedals are mechanically cycled 24 hours a day for up to several months while the data acquisition system records the position and monitors the motion profile to ensure the pedal is performing as designed. In some instances, stress is also measured on the component under test.
The original ATE system developed for this purpose as a custom solution was a proprietary non-standards based system no longer supported by its manufacturer. Later, the system was updated with VXI components from KineticSystems, but was still largely proprietary.
"Every time they purchased a new system they made incremental improvements, but never came up with a standardized solution they could easily duplicate," says Krebs. "Now they were interested in a more economical solution that took less real estate and that they could standardize globally."
KineticSystems was able to satisfy the requirements with a PXI-based solution. The company supplied 4 modular off-the-shelf instruments (KineticSystems Model #CP246) in rack mounted enclosure. Each CP246 is a flexible 8-channel CompactPCI/PXI module with signal conditioning and ADC.
To meet the needs of a specific application, instrument makers are often asked to semi-customize hardware, software, and firmware elements.
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 KineticSystems' configurable data acquisition software, SoftView, which provides access to all of an instrument's capabilities and features through a simple point-and-click GUI.
Laser Instrument Systems
There are several advantages of purchasing COTS modules: reduce costs, faster time-to-market and allow a company to focus its abilities on the design of the complete measurement system and not be concerned with test instrument manufacturing.
This was the case for a U.S. manufacturer of laser instrument systems for specialized inspection at electrical and geological sites. The manufacturer had been dedicating valuable resources to engineering its own digitizer card in house, which was expensive and time-consuming and distracted personnel from the company's core competence — the laser optical system itself.
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. GaGe, a manufacturer of high-speed PCI/PCIe digitizers, had just released one of the industries' first digitizers with FPGA programmability that performed many of the functions in firmware processing that the manufacturer required. After some research, the laser manufacturer selected a 12-bit high-speed digitizer from GaGe.
Almost immediately, it was clear that the FPGA was not large enough for the application, so GaGe worked with the customer to add another, larger FPGA. The larger FPGA was from the same FPGA family and was pin compatible with the original. Consequently, GaGe was able to enlarge the FPGA without changing the circuit board, which would have entailed much higher costs.
The manufacturer then realized belatedly that the digitizer they had developed in house was also equipped with low-speed A/D, D/A, I/O to capture analog temperature measurements, activate motors, and turn the various devices on and off.
To add these elements, GaGe partnered with KineticSystems to deliver what became a 2-board solution — the digitizer and a PXI DAQ data acquisition board from KineticSystems modified to operate from a USB port that provided the additional functions.
EM Compliance Systems
In another example from GaGe, a US manufacturer of electromagnetic (EM) compliance systems required an 8-bit high-speed digitizer. However, the customer required more memory than currently available on even the largest of GaGe's digitizers. This was an extraordinary requirement as GaGe offers some of the highest on-board memory in the industry, up to 4GS/s. But the customer still needed more.
GaGe met the requirement with a two-card solution, with each card's memory designed to fill in succession. Due to timing delays between cards, a special triggering signal was added to activate the second card when the first card was full. GaGe provided a procedure to figure out the delay between the two cards and provided its customer with custom software that could be used to easily align data acquisition between the two cards through a visual representation of the signals.
The application also required a subtle adjustment to the sampling rate in order to cover the system's entire EM frequency spectra. According to the Nyquist Theorem, the sampling rate must be at least twice the highest analog frequency for completely accurate analog-to-digital conversion (ADC) of the signal.
The GaGe card delivered a 2GS/s sampling rate, but the customer wanted to be able to accurately identify signal frequencies up to 1GS/s. To build in flexibility, the customer specified 2.1 to 2.2GS/s sampling rate for the card.
Because GaGe utilized fixed oscillators, it had to look elsewhere for a solution. Fortunately, GaGe's digitizers have a built-in 10MHz reference input as part of its standard reference circuitry that, multiplied by 200 provided the 2GS/s. GaGe modified the normally fixed reference input to be adjustable between 9 and 11MHz so the sampling rate could be tuned to 90-110 percent of 2GHz which delivered a 1.8 to 2.2GS/s sampling rate.
According to KineticSystems' Krebs, there is a limit to customization that should be expected from COTS products. "Once you get to the point of having a vendor create a new circuit board, you are really designing a fully custom product," says Krebs. "The expense goes way up, and you are no longer reaping the advantages of COTS modules."
The bottom line: 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.
Contact: Kinetic Systems, 900 North State St., Lockport, IL 60441
815-838-0005 fax: 815-838-4424 Web:
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