The value of highly accurate, automated, and measurable testing for medical devices cannot be overestimated. As devices become more complex, and patient care becomes increasingly personalized, it’s never been more essential to ensure that each medical device performs reliably and exactly to specifications. Realistically, the first, tenth, and hundredth device off the production line must perform identically, regardless of the test station operator or other test environment variables.
To achieve such important goals, it’s imperative that the test environment and infrastructure be well defined, highly structured, and automated as much as possible. Recently, Spacelabs Healthcare, Snoqualmie, WA, a vendor of innovative medical devices including telemetry, patient monitoring, and anesthesia delivery and ventilator systems, partnered with Averna Technologies, Montreal, Canada, a test engineering firm that specializes in producing multifunction, modular, and automated test stations for clients in multiple industries.
A Multiple Test Station Project
This collaborative initiative required the development of 10 different standalone test stations to validate the functionality of Spacelabs’ telemetry transmission and reception modules, as well as an anesthesia delivery and ventilator system, from printed circuit board (PCB) to final assembly testing. This article will focus on just one test station for a new product—the AriaTele transmitter, formerly Salish Telemetry Transmitter (STT)—in order to explain how Averna designed and implemented a next-generation test system to achieve Spacelabs’ goal of automating and accelerating its electrical-mechanical performance testing.
The STT, shown in Figure 1, transmits a patient’s electrocardiogram (ECG) and oxygen saturation (SpO2) data wirelessly from the patient to a remote monitoring station. This article documents Averna’s implementation of the test station for the STT units and covers instruments, fixtures, test architecture, and test management software, explaining how they combined to increase Spacelabs’ testing automation and device throughput. Other project benefits include a paperless test environment, centralized test package distribution, and database-driven test results and analytics.
Flexible Test System Design
With the wide range of products to be tested, Averna and Spacelabs decided early in the project to architect the multiple test stations based on standard 19-inch racks and, wherever possible, modular radio frequency (RF) test instruments, such as PXI and PXIe from National Instruments. For the test sequencing, Averna employed the manufacturing industry standard of NI TestStand and LabVIEW. In addition, application-specific instruments were implemented to recreate Spacelabs’ product environment. For example, the STT test station, shown in Figure 2, comprises an ECG simulator, an SpO2 simulator, and a telemetry receiver (a Spacelabs’ product functioning as a captive device) in order to produce the necessary real-world RF and medical data environment for testing each STT unit.
An Intelligent Fixture Holds the UUTs
To keep operator intervention to a minimum, the STT test station’s fixture features a custom sliding base plate that ensures easy unit loading/unloading, uniform unit under test (UUT) positioning and repeatable RF measurements. The fixture’s integrated RF capabilities, such as Bluetooth, antenna coupler, and a breakout circuit PCB assembly, enable testing the UUT over wired and wireless interfaces from 100 MHz to 5 GHz, ensuring reliable measurements. To prevent any situation that could alter the integrity of the RF propagation conditions, the fixture has a plexiglass cover that closes over the UUT during testing. (See Figure 3)
Automated Test Sequencing and Execution
Perhaps the greatest advances for Spacelabs’ test approach were achieved through the sophisticated test architecture that were designed and implemented on its test stations to validate all electrical and mechanical properties of each STT. Averna used a combination of NI TestStand and LabVIEW software to sequence more than 125 tests, which are set to run automatically. To ensure that the testing runs smoothly even when it encounters Bluetooth communication or runtime issues, the system includes automated error handling and retry capabilities.
The test phase starts when the operator scans the UUT’s barcode and places the UUT in the fixture. The system automatically recognizes the unit based on information in the test platform’s Proligent database and begins the predetermined NI TestStand test sequence. The testing takes 20 to 25 minutes per UUT and comprises seven stages, which the operator can observe on the test station’s attached monitor. They are:
- Boot-up Self-Tests – Once the UUT has been installed in the fixture, a power-on self-test takes place, followed by the validation of basic UUT functionality. For example, the system checks the voltage parameters and currents for all the device’s functional blocks, and verifies the self-tests and configuration states, including the hardware and firmware versions on the device. Based on the unit’s unique serial number, the test system then sets up the sales order configuration of the UUT, which is specified in the Proligent database. The system proceeds to upgrade the unit’s application firmware based on its model-specific features such as modulation bandwidth/scheme, number of ECG electrodes, medical features, and frequency band and channel.
- ECG Electrode Tests – Next, the system begins testing the medical functionality against the product specifications. In this case, it taps Spacelabs’ ECG simulator to verify the ECG electrode status and voltage of each electrode to ascertain the quality and magnitude of any stimuli or waveform transmitted through the STT’s ECG connector port. On the STT’s ECG electrode connector port, the system simulates human impedance to validate electrode presence and effectiveness.
- RF Tests – At this stage, the system makes frequency adjustments then performs RF power tests, followed by adjacent channel power using modulated signals, and spurious RF emissions such as in-band, out-of-band, and second and third harmonics.
- RF Data Integrity Tests – For this step, the system launches Spacelabs’ ECG simulator to generate an ECG vector, which the STT captures, modulates, and transmits to the telemetry captive receiver. This module demodulates the ECG vector and compares it to the original ECG vector, evaluating any deviation from the expected results.
- SpO2 Tests – For STT models having the SpO2 option, the system next engages the SpO2 simulator in order to generate measurements for the saturation of peripheral oxygen and heart rate.
- Button Tests – Once all of the above tests are successful, the system prompts the operator to test each of the unit’s buttons to validate appropriate behavior and to ensure that each input provides the expected system reaction.
- Final Tests – In the last round of tests, the system programs the unit’s sales order configuration such as channel, frequency, bandwidth and lead type.
Once the tests are completed, the system writes the results to the Proligent database, where they are stored based on the UUT’s serial number.
A Paperless Test Environment
One of the main goals of the project was to substantially limit operator interactions with the test station and test routines in order to eliminate the impact of the operator on test results. That was achieved using automated sequencing and a paperless test environment. The few test steps requiring operator interactions, such as the manual testing of the device’s buttons, are dictated by screen prompts.
Due to the rigid, automated test sequencing, every unit is strictly subjected to the same tests in the same order, thus no shop floor improvisation is permitted. In fact, operators never touch the test station, its instruments, or cabling, and cannot modify test settings or skip steps, eliminating test result variability and the possibility of human error.
Automating Inbound and Outbound Data
Central to Averna’s test architecture design is the automation of inbound and outbound test station data. More specifically, inbound data (e.g., Spacelabs’ test routines/ packages) and outbound data (UUT test results) are managed by Averna’s Proligent test data management software.
For inbound test data, Spacelabs’ test engineers use Proligent’s Test Package Manager module to define and version the test packages that are transferred via an internal network directly to the test stations, regardless of the stations’ physical location. Thus, by automating and synchronizing test package updates, all test stations always have the same tests, firmware, drivers, and documentation, significantly reducing the chances that units tested at different facilities might be tested with different tools or criteria.
For outbound data, Spacelabs uses Proligent Analytics, an automated module that gathers, aggregates and stores all test results in a central database, where they can be accessed via more than 50 reports and charts. As well, Proligent Analytics provides a multi-dimensional view of the data, letting Spacelabs’ test engineers quickly drill down to examine any unit- or batch based test results, product component- or supply chain-related issues.
As designed, Spacelabs’ new test stations are highly streamlined and require few operator inputs, which has improved testing efficiency and throughput for the company’s telemetry products. As well, since the test systems are based on a design that includes a flexible test executive (NI TestStand), swappable fixtures, standard racks with 20 percent extra space, and centralized test data management, Spacelabs will be able to easily update its systems over the coming years to cover new and evolving product features, protecting its test infrastructure investment.
This article was written by Yvon Lemyre, RF Test Engineer, and Alexandre Boyer, Team Leader – System Architecture, Averna Technologies, Montreal, Canada, and Eric Soshea, Operations Engineer, Spacelabs Healthcare, Snoqualmie, WA. For information on Averna Technologies, visit averna.com . For more information on Spacelabs Healthcare, visit spacelabshealthcare.com .