Using LabVIEW, NI TestStand, and PXI to Test a Medical Glucose Meter and Insulin Delivery System Within a Regulated Manufacturing Environment
"The NI solution provided numerous benefits for this application. First, the NI VSA/VSG solution was significantly faster than the boxed instrument equivalent – the testing would have taken several minutes longer if traditional boxed instruments were used."
- Venkat Raghavan,
Developing a set of production testers, including an RF communication test, for the subcomponents of an FDA Class II medical glucose meter and insulin delivery system under aggressive development deadlines.
Using NI LabVIEW software, the NI Spectral Measurements Toolkit, NI TestStand, and NI PXI RF hardware to develop fast, repeatable tests.
Advanced Instrument Technologies, Inc. (AIT) is an engineering services company providing custom and turnkey solutions to meet customers’ test engineering challenges. AIT provides customers with services ranging from engineering support to complete solutions. AIT serves customers in numerous industries, covering research and development, manufacturing, and quality assurance testing. AIT has been a National Instruments Alliance Partner since 2003. AIT was chosen to work on this application because of its previous positive experiences with the contract manufacturer and the company’s years of experience engineering with NI hardware and software. For this project, AIT developed the software and assisted in hardware design.
TestPro Systems, Inc. is an engineering services company organized to support engineering departments with test and new product introduction (NPI). TestPro provides services and solutions for functional fixtures and programs as well as fully automatic functional test platforms. TestPro Systems typically caters to customers in the automotive, medical, and energy industries. TestPro Systems was chosen for this task because the company previously developed several functional fixtures for the contract manufacturer and has extensive experience with LabVIEW. TestPro was contracted to help with some of the system design and wiring. Due to scheduling demands, TestPro also assisted with the development of the base LabVIEW code and NI TestStand sequences.
The devices under test (DUTs) are components of a medical glucose meter and insulin delivery system. The DUTs includes a user panel, a meter on which the user panel mounts, and an insulin delivery actuator. The meter communicates with the actuator to pump insulin as required. Each component is tested on a separate test system.
The meter and pump communicate wirelessly using proprietary encrypted RF messaging within the medical wireless bands. The DUTs RF signals must be tested for output power, and the system must simulate the RF messaging to verify the DUTs can properly receive and decrypt messages. The DUTs also contain a 32.768 kHz and 16 MHz clock that need to be tested. The customer specification required the 32.768 kHz clock to be accurate to 60 ppm and the 16 MHz clock to be accurate to 22 ppm.
The system must use a repeatable, traceable signal each time the DUTs RF reception is tested. The signal analyzer must be repeatable and accurate for testing the DUTs RF transmissions. To keep test times to a minimum, most of the analysis must be performed using the hardware.
Most tests involve turning an output on or off using serial peripheral interface (SPI) communication and then measuring the state or level of an output. However, the most critical tests verify RF communication and the critical clocks on the meter and actuator.
When testing the transmit functions on the DUT, the DUT is commanded to transmit RF test data packets and RF spectral analysis must be performed to check the parameters of the transmitted signals. When testing the receive functions on the DUT, RF data packets must be transmitted by the tester and the unit must be queried to verify the RF packets were received. To test the clocks, the clocks need to be enabled and measured.
Although AIT considered a box spectrum analyzer and RF capture system for the RF testing, and a high-end frequency counter for the critical clock tests, the NI solution was chosen for several reasons. The NI PXI-5661 vector signal analyzer (VSA) and the NI PXIe-5672 vector signal generator (VSG) combination could handle all the required tests while smoothly integrating with LabVIEW. The VSA/VSG combination hardware was less expensive and required less space than the boxed instrument solution. We could also use numerous NI provided key LabVIEW examples for the application, such as streaming RF record and playback, which made integration much easier and faster.
An NI PXIe-1065 chassis contained all the instrumentation for the complete test system. In particular, three NI PXI-6229 M Series data acquisition devices were used to provide all the digital I/O, perform SPI communication using hardware timing, measure analog voltages, and generate analog voltages.
A PXI-5661 along with the NI Spectral Measurements Toolkit, performed the signal analysis. The VSA along with the streaming RF record technology was used to capture the transmitted RF messages from a gold DUT and save the data to a file. The VSA, with its 50 ppb accurate timebase, was used to measure the critical device clocks. An NI PXIe-5672 used the streaming RF playback technology to transmit the captured RF messages to the DUT from the previously saved data file.
National Instruments provided critical help with the VSA/VSG solution. NI provided a LabVIEW example program with source code demonstrating the streaming RF record and playback capabilities, which was leveraged in the final solution. Additionally, NI engineers assisted with consultation on the critical clock measurements.
The NI solution provided numerous benefits for this application. First, the NI VSA/VSG solution was significantly faster than the boxed instrument equivalent – the testing would have taken several minutes longer if traditional boxed instruments were used. Second, development time was greatly reduced by using familiar products with superb examples that directly applied to this use case.
Third, we developed LabVIEW core code modules, which could be reused in multiple NI TestStand test sequence steps. The added benefit of this code is the potential reuse in future projects. NI TestStand helped greatly simplify the verification and validation of code and test sequences. NI TestStand also provided consistent operator interfaces, which minimized training time as required for quality control and CFR Part 11 compliance.
NI tools also helped us comply with requirements such as 21 CFR parts 820 and 11, which govern the creation of systems to test medical devices. Additionally, NI tools helped us examine system design under standards such as ISO 13485 and ISO 14971, which provide mechanisms and processes to meet quality and risk management regulations.
Finally, LabVIEW software and the supported toolkits lend themselves to creation of the installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ) documentation reports.
AIT and TestPro were very satisfied with the NI products and services provided. The NI support was critical to the success of the project.
A National Instruments Alliance Partner is a business entity independent from National Instruments and has no agency, partnership, or joint-venture relationship with National Instruments.
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