DMC's client had an urgent need to replace their slow, error prone manual production test procedure, but they did not have complete test specifications or requirements for a solution to replace it. Being a lean startup, they needed support to complete a test specification within their timeline rather than wait to develop requirements and a full test specification internally.
The manufacturer approached DMC as soon as they identified the basic needs and challenges and chose us based on our demonstrated knowledge and experience testing similar products in the electrification sector.
DMC first took on a consulting role, leveraging decades of test engineering and technical expertise to collect and assess their requirements. Then, we collaboratively balanced the project tradeoffs (schedule, budget, risk, quality) against the technical performance of the new test system: resulting in a well-informed test specification and a conceptual test system design.
This collaborative ‘design phase’ quickly set up the entire project for success. The design phase uncovered several hidden requirements upfront, which resulted in faster convergence on the best test solution and allowed for continuous improvement with the flexibility to incorporate more complex quality assurance testing when they are needed.
The following ‘design/build/deploy phase’ used DMC’s standard ‘turn-key’ project process, resulting in the successful deployment of the client’s new automated test solution in their production facility within a few months.
Technical Details
The client’s product was designed to safely store hundreds of kilowatt-hours of energy in an internal battery system and provide that power to users in a variety of AC-power formats through several physical outlet options. It also featured a user-friendly touch-panel display for configuring the AC power output.
In their previous manual process, testing these units required operators with technical expertise, physical dexterity, and test instrumentation skills. The manual testing process involved taking numerous measurements to ensure they met specific manufacturing standards while repeatedly interacting with various knobs and switches in a predefined manner. It also involved the risk of manual probing into a high voltage receptacle.
Test System Architecture:
DMC physically assembled high-speed and high-precision instruments into a small-form-factor test rack, along with an industrial PC and peripherals, an AC power distribution unit, and a single main test signal distribution/breakout panel. The industrial PC acts as the single test controller and communicates with test instrumentation through a variety of communication busses (Ethernet, RS232, USB).
Test System Hardware:
Pickering High Voltage Multiplexer: Instead of requiring an operator connect and disconnect various parts of the test system with the high voltage connections of the device under test, a set of Pickering high-voltage, relay-based multiplexer cards were housed in an LXI chassis and used to automate the voltage switching functions. This allowed a custom software layer to manage all the switching connections.
Keysight DMM: Making accurate voltage and resistance measurements in quick succession meant using a robust DMM that could handle such usage. Selecting a benchtop-style instrument, connected over ethernet using the LXI standard, allowed DMC to strike a balance between performance and cost. As a bonus to having a highly-flexible DMM integrated into the system, DMC designed an automated self-test sequence: which used the DMM to verify the health and integrity of the test system itself.
NI-XNET Interface and NI cDAQ: To monitor for faults and unexpected behavior, the test system listened to the machine’s internal CAN bus using robust NI XNET hardware integrated into a cost-conscious NI cDAQ chassis and connected to the PC controller over ethernet.
Test SystemSoftware
NI TestStand: To allow the client’s test engineers to quickly modify test sequences, or develop new ones, we created custom test steps that allow drag-and-drop usage and rearrangement within the intuitive and powerful interface that TestStand provides. The built-in test report functionality of TestStand was also utilized to produce customized reports for every device tested.
Operator Interface: DMC's leadership in the Test & Measurement industry comes with plenty of internal tooling, which saves development time and associated costs for customers. One of these tools is LabVIEW code that provides a simple user interface which connects to TestStand, presenting a simplified HMI experience for operators. The system allows for different types of products to be tested with different test sequences by simply scanning a barcode on the product prior to starting a test run.
Python Drivers: The DMC software team used the inter-operability features of TestStand to call Python hardware drivers. Python allowed the DMC team to easily integrate publicly available and instrument vendor provided packages, merge code, and review code from multiple developers. This freed up the team to focus on simplifying the end user experience with easy-to-use test steps that included signal multiplexing and instrument acquisition.
End Result
DMC’s system design effort automated nearly every step of the new testing process, reducing operator steps and limiting the client's exposure to energized high-voltage connections. The test solution continuously monitors for issues, faults, and unexpected behavior within the product's internal control system. A clean and simplified test interface allows operators to focus on quality, following clear, specific instructions to interact with the machine's front panel, reducing the risk of errors, and significantly speeding up the testing process.
While the previous manual test system took 1.5 hours per unit tested, the new automated test system can complete a full product test in under 2 minutes. Every aspect of the test process, from checking the CAN bus for faults, probing every electrical outlet for proper voltage, or running load tests, is now fully traceable, accurately recorded, safer, and faster with the new DMC test solution.
Learn more about DMC's Automated Test Stand Design services and contact us for your next project.