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Designing a home health care monitoring device

09 May 2016  | Gwyneth Saldanha

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By the end of the project, Nuvation had conducted the compliance testing and certification required to meet all regulatory standards in the areas of Telecoms, Safety, and EMC, certifying the client's device to a combined total of twelve industry standards and their sub-part.


Radiated, conducted and electrostatic discharge
A variety of innovative approaches were required to design a product compliant with all applicable medical device, telecommunications and radio interference standards. Part of the challenge involved accommodating an innovative industrial design that required connecting three boards with flat-flex cables within a plastic enclosure. This increased the risk of radiated, conducted, and electrostatic discharge (ESD) because of the possibility of high frequency noise radiation emanating from the flat flex-cables when devices were connected to the USB ports. Nuvation resolved this vulnerability by adding suppression components to the signal lines at every off-system connector and adding more filter capacitance to the signal lines.

Selecting a power supply with a common mode noise level that does not exceed regulatory limits was a critical factor in meeting the IEC 60601-1 and FCC Part 68 standards for telecoms and radio interference. Power supply vendors do not state their products' common mode noise specifications on their datasheets, so Nuvation lab-tested various power supplies. Testing revealed that several low-cost power supplies from offshore suppliers exceeded the FCC-mandated limits despite claims of being "medical grade." After testing numerous power supplies one was found that was both compliant and within the target price range.


Figure 2: Nuvation's concurrent Integrated Design to Manufacturing (IDM) process can shorten the project schedule by as much as 30%.


Mitigating component obsolescence
The client's existing device utilised components that were nearing obsolescence. This was driving up production costs by requiring volume purchases of near end of life (EOL) components to support continued production. Nuvation leveraged their partnerships with component manufacturers to ensure that all components selected for the new device would be available well beyond the planned lifecycle of the new product.


Meeting target production costs
The client was hoping this next-generation product could be produced at a lower price than its predecessor. During the discovery phase of the project however, Nuvation determined that the hardware and software components required to support the functional requirements would in fact make the product more expensive. Cost drivers included requirements for an Android operating system, a telephone line interface, colour LCD screen, and the ability to power the device from both standard cell batteries and an AC adapter. The Android OS requirement for example, limited the type of CPU that could be selected and imposed a minimum memory requirement on the design, and supporting POTS required a telephone modem.

After weighing the options of accepting the higher price point against reducing the functionality, the client determined that their customers would prefer the full functionality and still respond positively to the revised price. Nuvation managed to keep the new price within the client's budget by thoroughly reviewing the system architecture and negotiating with component suppliers on the client's behalf. They were able to find a newly developed integrated CPU and modem that cost 75% less than discrete components would have, and leverage their partner network to obtain extra discounts on components.


From design to manufacture
With the product designed, tested, and meeting all regulatory requirements, it was time to take it to production. Where many design firms consider this the point of "hand-off" to the client, Nuvation's turnkey services include managing the transition to volume manufacturing. Nuvation designed a manufacturing test fixture to validate the product assembly process, creating a "bed of nails" style fixture and functional test program that verified the hardware and software functionality. They also wrote a test manual and provided onsite training to the contract manufacturer. When production began, Nuvation continued supporting and debugging issues during small pilot production runs until the transition to volume production was complete.


Designing for the end-user
Nuvation worked with their industrial design partners to deliver a visually appealing and compact industrial design for this home-use medical device. The design included a 3" LCD screen that supported large fonts and colourful graphics for easy viewing and operation, and a small amount of large buttons with dedicated functions that made it very easy to use. They also engineered the product to deliver a battery life of 3-6 months, making it virtually maintenance-free.

Key elements that made this project a success:

 • Strong communication between the client and engineering team during all phases of the project
 • Up-front "Phase 0" discovery phase that provided the client with full visibility into the project scope and "all-in" costs. This enabled the identification and resolution of potential issues before work began
 • A diversely experienced software and hardware team supported by a collaborative workflow process
 • A technology partner network that enabled the engineering team to source the best products and obtain the lowest available price points to meet the client's needs


References
[1] Continua Health Alliance and Associated Standards, Accessed April 23, 2015

[2] Understanding the impact of 60601 3rd edition on power design, Accessed April 23, 2015

[3] FCC Part 68, Accessed April 23, 2015

[4] Innovation, Science and Economic Development Canada, Accessed April 23, 2015

[5] TBR 21 guideline, ETSI, Accessed May 4, 2015.

[6] CISPR: International Special Committee on Radio Interference, Accessed April 23, 2015


About the author
Gwyneth Saldanha is the Engineering Operations Manager at Nuvation Engineering.


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