By Nigel Adams, Senior Product Specialist, Aeroflex Inc
In the modern world, the need for accurate testing and measurement is paramount, and is more important than ever where the items under test have an application in a medical environment. The lists of approvals and compliances are immense and must be followed rigidly to ensure acceptance by some administrations. Not only should the item be tested to specific criteria, but it also must be seen to have passed this arduous process by extensive recording of both results and processes. Official agencies, such as the U. S. Food & Drug Administration lay down particular requirements in this arena and anyone who does not meet the standard will not be licensed to offer its product to the market the agency oversees.
Huntleigh Healthcare is a market leader in the world of medical screening products and other medical facilities from steriles to beds. Recently, they introduced Multi-Dopplex, a new product in the form of a hand-held Doppler sound scanner and blood flow analyzer (see Figure 1). This scanner offers Huntleigh a chance to provide a world class solution to the marketplace. The unit has two variants and a number of probe options to provide functionality, providing a testing challenge.
Increasing test complexity To test the Multi-Dopplex, designers originally conceived a PCI solution that offered functional test only. However, as the test teams looked at the possibilities, they revised and enhanced the test platform and strategy to offer a depth of test that could provide both analog in-circuit and functional test capability from a single application.
The analog test capability was critical. Very specific measurements were needed to ensure that all the probe types would perform correctly with the hand-held parent unit. In the case of the fetal probe unit there was a specific check to ensure a waveform input was clipped correctly. Checks on the unit power consumption and voltage levels were required, especially important to ensure that a failing battery or low supply would warn the operator prior to any actual measurements being compromised.
A traditional PXI-based solution may have provided the appropriate instrumentation and digital input control functionality, but could not offer the analog in-circuit capability in the standard enclosures. Huntleigh selected Aeroflex as the supplier for this project, choosing a full 21-slot PXI backplane that combined both the standard card PXI types as well as comprehensive in-circuit utilities. We used a traditional type of 'bed-of-nails' fixture through a 'pylon' style interface to connect to the Aeroflex 5800 Series. Where required for signal integrity we used twisted pair and screened cable wiring. A number of small signal conditioning circuits were mounted to the base of the fixture bed so as to be close to the interface to the UUT.
The main reason for choosing the 5800 over a straight PXI solution was the need for fast, accurate in-circuit measurement, which cannot be gained through traditional PXI utilities. Specifically, the fast continuity and analog measurement capability was a must have on this application and on a number of custom routine for potentiometer measurements. Much of this capability is achieved through a fast and flexible switching matrix. Although other PXI switches exist, they do not meet the specific in-circuit requirement. In particular, we have access to a configurable analog and digital highway on the system backplane, which is not available in standard PXI racks.
Wrapping software While the revised test solutions provided adequate levels of test, the need for a process that could evolve with the product was required. This called for a modular system that could accept changes in test resources without having to completely rewrite the test procedure or re-engineer the code into another test language.
Many companies have engineers whose skill sets embrace program development in many of the popular test languages: LabVIEW, Visual Basic™, and C#, along with test executives such as TestStand™. This provides a rich seam of code blocks that should benefit from re-use in subsequent applications, but rarely do. The benefit of using previously proven code in new designs offers advantages in terms of time to market and cost effective test.
Available within the Aeroflex proprietary test executive is a wrapper tool that can take code and create a fully compliant .NET utility that could then be called directly into the main program code. This can save valuable time in creating functions that could be recalled as libraries.
In the Huntleigh application, the original LabVIEW™ code was compiled into a .DLL and then integrated using the new DLL wrapper tool (see Figures 3 and 4). Further leverage was gained by reusing code segments that were already in the production test process, along with new structures that could be called through the .NET capable test executive.
Managing the data The Multi-Dopplex module could now be in-circuit tested with full accuracy at a fast speed and directly follow into functional test if the ICT was successful—all of which could be executed on a single system and in full compliance of the test procedure. Additionally, the full result logging of both test segments could be captured in an i-Base5 data collection and analysis system, along with all the important test process details regarding test systems used, the operator details, batch numbers and date/time functions, and more. With this data captured, a complete test history could be instantly recalled if required for audit or investigative purposes, which is handy for potential compliance or litigation issues.
The complexity of modern electronic devices coupled with the requirement for ever-increasing reliability means that traditional approaches to test are not always sufficient. The changing face of combinational test is beyond the expertise of most test equipment vendors. The 5800 Series draws on the expertise of one of the longest established test companies, as well as the knowledge and expertise of a plethora of external equipment and software suppliers. This combinational test platform is poised to tackle the industry’s toughest testing challenges, today and tomorrow.
Author information Nigel Adams is a senior product specialist for ATE products and i-Base Data Collection software with over 32 years of service.. He joined Marconi Instruments in 1975 and transferred from Instruments to ATE systems in 1984, working in service and support management roles as Marconi was acquired by IFR in 1998 and subsequently Aeroflex Inc. in 2002. He holds a Higher National Certificate in Electronics, and a Higher National Diploma in Electronics and Radio from Hatfield Polytechnic, Hatfield, U.K.
