Modular instruments make light of medical tests

Sanmina-SCI, one of the world's leading contract manufacturers, selected PXI modular instruments and test management software from National Instruments to develop an FDA-approved production tester for testing and calibrating medical devices that measure blood glucose levels.

"The NI test platform delivered the accuracy and flexibility we needed to quickly build a compact test system that exceeds our throughput requirements of testing 83,000 devices per week while maintaining a cycle time of 30 seconds per device, and exceeds our yield requirements with production yields greater than 95%", said Mike Oehrlein, Sanmina-SCI Senior Staff Engineer.

The PXI-based system tests a medical device that measures blood glucose levels by performing measurements of the current and impedance characteristics produced from an electrochemical reaction.

The system calibrates the DC amplifier circuits of the measurement engine and verifies the operation of other critical support circuits contained within the device under test.

In addition, the system switches various input loads into the measurement engine to emulate the complex task of simulating the blood response.

Sanmina-SCI had traditionally used GPIB-based rack and stack instrumentation systems, but due to the high throughput requirements of the system, the company chose a hybrid test system based on PXI modular instruments and GPIB.

The test system hardware is based on NI PXI-4070 6.5-digit FlexDMMs for voltage and current measurements, NI PXI-6533 high-speed digital I/O modules to communicate to the device under test and write the calibration values to the onboard EEPROM, an NI PXI-6508 general-purpose digital I/O module and an NI PXI-1045 chassis.

The PXI platform delivered the throughput and accuracy needed to make all of the measurements on the device under test while still exceeding the company's yield goals.

Sanmina-SCI chose NI TestStand test management software because it provided test sequencing of LabWindows/CVI and C#.NET modules, native parallel testing support and a custom software interface with strict user management for administrators, supervisors, engineers and manufacturing operators.

The company used NI LabWindows/CVI for test module development because of the built-in test and measurement functions and user interface controls, as well as the SQL database connectivity capabilities.

With LabWindows/CVI, the software developers created highly efficient ANSI C source code that integrated with modular instruments and GPIB.

By using commercially available software, such as LabWindows/CVI and NI TestStand, Sanmina-SCI kept software development time and costs to a minimum.