Multi-PCBA Functional Test for FDA Compliance

Project Summary

Cyth developed a unified test platform using PXI, LabVIEW, and TestStand spanning test plans, fixturing, and a common automation architecture for six PCBAs used in patient monitoring devices.

System Features & Components

• PXI instrumentation mapped to multi-DUT test coverage

• Custom fixturing for 6 constituent PCBAs, including bed-of-nails connectivity to test points

• RF environmental enclosure for wireless test

• Measurement software (LabVIEW) and test automation executive (TestStand) with a common architecture for efficient reuse across devices-under-test (DUTs)

Outcomes

• Minimized capital costs through instrumentation configurations shared across devices-under-test

• Reduced engineering development and maintenance effort with common measuremeent code and test automation software

• Successfully achieved schedule milestones for factory acceptance testing (FAT)

  
  

Technology at-a-glance

• PXIe Chassis: PXIe-1078

• Data acquisition: PXI-6229

• Sensors and signal conditioning: pressure transducer, digital signal attenuator, programmable DC loads

• Power: PXIe-4112 and PXIe-4113 programmable power supplies

• Switching: PXI-2564 SPST relay module and PXI-2534 matrix switch

• Serial communication: PXI-8432 RS232 interface module

• Environmental: RF Faraday enclosure

• Test automation software: LabVIEW and TestStand

Enabling Responsive Patient Care

Vital signs monitoring equipment is the quiet workhorse of patient care. These systems take critical physiological measurements, such as temperature, respiratory rate, blood oxygenation, and blood pressure, to provide clinicians with quantifiable data to assess patient health status and automatically detect changes that may indicate emergencies requiring active intervention.

Like many medical devices and hospital equipment, modern vital signs monitors have evolved from simple measurement devices to sophisticated digital systems capable of continuous monitoring, wireless data transmission, and integration with electronic health records (EHRs), enabling more responsive patient care and improved clinical outcomes. While these products have become more intelligent and automated, the need for rigorous testing across design and production phases continues to grow.

Enhanced Visibility & Monitoring

The product incorporates four vital measurements across two distinct measurement subsystems:

• Cuff attached to the patient’s arm – measures systolic and diastolic blood pressure

• Pulse oximeter clipped to the patient’s finger – measures oxygen levels, heart rate, and temperature

These subsystems are physically connected to a processing and display unit. The system is also capable of transmitting patient readings wirelessly and securely to local devices, such as a nurse’s tablet, for enhanced visibility and monitoring.

Comprehensive Test Coverage

The engineering team responsible for testing the product faced several core challenges:

• Finding a test solution that would provide comprehensive test coverage for six individual PCBAs and final assembly verification

• RF testing for wireless connectivity in a controlled, interference-free environment

• Reproducible and reliable test data for FDA approval and ongoing compliance requirements

They were looking for outside help from an engineering firm experienced with PCBA and final assembly functional test, ranging from fixture design, instrumentation selection, and connectivity, to test software development.

Designing a Unified Test Platform

After engaging with the client on the product's test requirements, budget, and timeline, the Cyth engineering team started by mapping the intended test coverage to instrumentation capable of performing the measurements. They recognized an opportunity to optimize footprint and overall hardware utilization by consolidating the various DUTs into three bed-of-nails fixtures and two test enclosures. This allowed us to refine the hardware BOM, lowering overall cost spread across the DUTs.

PXIe Instrumentation

• PXIe Chassis: PXIe-1078

• Data acquisition: PXI-6229

• Power: PXIe-4112 and PXIe-4113 programmable power supplies

• Switching: PXI-2564 SPST relay module and PXI-2534 matrix switch

• Serial communication: PXI-8432 RS232 interface module

After finalizing the instrumentation BOM, our team planned out the signal routing diagram, including strategic switching, from the PXI modules' channels all the way to the DUTs' test points, as accessed through cabling and the fixtures' pogo pins. Throughout this process, we leveraged our PCBACheck ATE platform for advanced starting points on fixture CAD, layout, and sub-components.

In effect, this versatile test fixture design allowed for multiple DUTs to be tested simultaneously, increasing the throughput and efficiency of the system without requiring additional instrumentation.

Environmental RF Test

One of the more complex challenges involved validating the product's wireless interface. To do so, the ATE development team needed to create a controlled environment free of RF noise and interference, opting to design in an RF Faraday enclosure to create such an environment.

The Cyth team developed a comprehensive test protocol that exercised the wireless PCBA across multiple power modes using a 3-bit control signal. Through a digital signal attenuator, we measured transmission power and signal quality across the ISM Band (Industrial, Scientific, and Medical), specifically at 838 MHz and 916 MHz frequencies. This test methodology supported the project requirements of:

• Validating signal strength at various Tx/Rx distances

• Verifying proper power mode transitions

• Documenting signal quality metrics for regulatory compliance

Test Software & Regulatory Compliance

The Cyth team developed the test software in conjunction with the hardware design and build aspects of the project. Using our PCBACheck software framework, we developed individual test modules in LabVIEW using a hardware abstraction layer in the form of driver APIs and pre-existing measurement expertise. From there, we incorporated those discrete, reusable code modules into multiple NI TestStand sequences capable of executing the test plan for each individual DUT. NI TestStand and the PCBACheck automation framework for functional test provide the following benefits:

• Test sequence development – graphical sequence editor for code module integration and validation against test requirements

• Test execution – flexible process models and multi-threaded resource management

• Data access – customizable operator interfaces, report generation, and database connectivity

Implementing a unified test automation framework across the DUTs helped with code reuse, debugging, and test data repeatability. Having reliable, consistently formatted test data helped our client with their Factory Acceptance Test (FAT) phase and lowered the effort to collect and report on compliance metrics for the FDA, avoiding many hidden costs and unpredictable headaches.

Full Turnkey Test Coverage

Overall, the Cyth team delivered a complete turnkey solution of two PCBA functional test enclosures and a final assembly test for our client's patient monitoring product within schedule and budget.

The unified test platform provided a versatile fixture design and intelligent instrumentation routing, helping control capital equipment costs. The test automation software provided full test coverage for the various individual DUTs, making test data easily accessible and repeatable.

In effect, this solution helped our client spin up their factory test capabilities sooner than an in-house approach, clearing the product's path to market and easing downstream quality control efforts.