Cochlear Creates Hearing Implant Test System Using NI TestStand, LabVIEW, and PXI

Author(s):
Paul Carter - Cochlear Ltd.

Industry:
Medical/ Medical Instrumentation

Products:
LabVIEW, PXI/CompactPCI, TestStand

The Challenge:
Reducing escalating costs and development time for a new generation of hearing implants by creating an automated, mixed-signal test system using off-the-shelf technology.

The Solution:
Using National Instruments LabVIEW, PXI computer-based instruments, and NI TestStand to create a suite of automated test systems that provide greater flexibility and functionality with 30 percent less development time.

Designing an Efficient Test System

Cochlear Ltd. in Sydney, Australia, is a world leader in the technology of implantable hearing devices, bringing the joy of hearing to thousands of people worldwide with severe to profound hearing loss. Our flagship product is the Nucleus cochlear implant system, which comprises an internal implant and an external speech processor. The speech processor analyzes and digitizes sounds into coded signals, which are transmitted to the implant by an RF signal. The implant converts the signals into electrical pulses, which are then used to directly stimulate the cochlear nerve fibers to produce a hearing sensation. We uniquely program each speech processor to meet individual hearing needs, which helps most recipients lead a normal life.

We pay close attention to product quality and safety, and this has helped us maintain our leadership position in the market. Because test systems play a key role in ensuring quality and safety, we turned to NI to help solve the test problems for our latest range of hearing technology. Our implant systems are complex and involve many different parts and subsystems. And our development of test systems for all these components can amount to a huge amount of time and resources - time we do not have.

As our products evolve, they become more complex and contain more components. With the constraints of increased quality targets and reduced production and test time, we needed a new test system that could perform. Traditionally, we developed all our test solutions in house using custom-built hardware and software. This worked for the simpler products, but we experienced increased difficulty getting test systems ready in time for product launches. We realized that for our latest product under development, the task had become too large to even contemplate in the time available using our traditional methods. So, we started to look for another way, using commercial, off-the-shelf technology.

With thousands of system sales annually, we operate in a market that is rapidly evolving from a niche application into accepted mainstream medical technology. We had outgrown a DIY test approach but were not prepared to invest in a multimillion dollar test system. The PXI solution has proved top be the best solution for a flexible test system at an affordable price. It offers quality, fully verified hardware and powerful software all at a reasonable price.

We use the new PXI-based functional test systems for in-house development testing across eight different applications from open boards to fully assembled units. We also use the system to do production tests internally and with various contract manufacturers. The system is required to perform a variety of actions including capture, storage, and analysis of the wave shape of a 5 MHz signal, which is used to transfer power and data across the skin to the implant. We used audio measurements, parametric measurement of voltages, and currents under various load conditions, digital I/O, serial, and GPIB to talk with external devices. We used USB communications to control relays, switches, and other hardware on the custom board. The system also needs to accurately tune a resonant circuit and test I2C communications. The system generates test reports on paper, but the data is also stored on the network for later statistical analysis. A local National Instruments Alliance Partner, CPE Systems, provided assistance with developing custom interface cards and software development expertise in LabVIEW and NI TestStand.

The test system comprises a PXI-based Pentium 4 controller with GPIB interface, NI PXI-4070 FlexDMM card, NI PXI-6052E multifunction data acquisition (DAQ) card, and an NI PXI-5112 high-speed digitizers. The DAQ, FlexDMM cards, and high-speed digitizers provide all the analog and digital input and outputs required for measuring mixed signal parameters and switching of signals. A conditioning amplifier is controlled by RS232 communications and USB controls another custom interface card. Smaller than any previous test systems, the new system saves precious space on the production floor. The PXI platform means the system is flexible, easy to service and easily updatable in the future.

Creating a Flexible Software Architecture

Using NI LabVIEW and NI TestStand, we developed a flexible software architecture to address our current and future test requirements. The software is versatile enough to test different versions of products and open and closed versions of hardware. Using NI TestStand, we saved development time with off-the-shelf test executive functionality.

Using a custom operator interface, an operator logs in, loads a selected test sequence, and monitors the testing as it progresses. The interface also provides real-time information updates to the operator, generates a test report, and logs all test information to a database for future analysis. We wrote the individual tests in LabVIEW, which also reduced development time because of the extensive libraries available for taking measurements, interfacing to hardware, analyzing results, and presenting data. By modularizing and separating the operator interface sequence control from the individual test modules, we can use the development effort across multiple products with similar test requirements. Having all the data logged to disk in a standardized format, our R&D and production engineers can mine the data for trends and generate reports on production yields. They also use the data to analyze failures and identify areas for improvement in the device manufacturing. The logging records contain all test information including the sequences used, parameters, calibration dates of instruments used for the tests, test time, and pass/fail status of the units.

NI TestStand Provides Results

The new functional test system helped us meet aggressive schedules to push new product designs from conception to manufacturing. NI TestStand has been invaluable to us in creating a modular, reusable test framework for our LabVIEW test modules. From a project perspective, we are now able to develop test systems in record time because much of the risk associated with hardware and software development has been taken out of the project. Our initial investment in training was recouped by reducing the development time for this project alone. In future projects, we expect to see around 30 percent less development time now that our engineers are comfortable with using the tools.  

For more information, contact:

Paul Carter

Senior Project Manager

Cochlear Ltd.

14 Mars Rd.

Lane Cove NSW 2006

Australia

Tel: +61 2 9925 5276

Fax: +61 2 9428 6335

E-mail: pcarter@cochlear.com.au

 

 

 

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