Medical Device Battery test using SMBus

Batery_Test_Main

Overview

Medical Device Battery test using SMBus. A medical device company needed a system to automatically test a battery that powered various medical devices. The software had to use existing Keysight instruments, and communicated to the battery under test via SMBus. The software needed to be simple to use and needed to generate a printed report for quality and regulatory purposes.

Solution

Hardware Block Diagram

We developed a program in LabVIEW that automatically tested the battery. Using the existing Keysight 3490 Data Acquisition Unit, the Keysight 3644 Power Supply and the BK Precision 8500 Electrical Load we were able to use already calibrated and approved measurement devices. This saved the customer from validating new measurement hardware. Validating hardware used in medical device testing is very rigorous. Using already validated hardware save the customer an enormous amount of time and money.

85xx front lrg 1

BK Precision 8500 Programable DC Electrical Load

Communication from the PC to the instruments was done using GPIB and USB. GPIB stands for General Purpose Interface Bus. This bus is used on a lot of test and measurement hardware and allows the hardware to be connected to a PC. NI has an extensive library of LabVIEW GPIB drivers that can communicate to hundreds of instruments.

NI GPIB

NI USB GPIB

SMBus was used to communicate to the battery under test. The System Management Bus (SMBus) is more or less a derivative of the I2C bus. The main application of the SMBus is to monitor critical parameters on PC motherboards and in embedded systems. We used a NI USB-8451 I2C/SPI Interface device that communicated to the PC via USB.

SMBus Module

NI USB-8451

Features

The user could choose to run all the tests or select 1 individual test to run. Each test was a series of commands and readings made on the battery under test. For example the software would send a command to the battery via SMBus and then read a voltage on the battery that was connected to the Keysight data acquisition unit. The software would then compare the measured voltage to a range read from a configuration file. If the measured voltage was outside the range the test failed. If the measured voltage was within the range the test passed.

The test software contained a human readable configuration file that allowed the engineer to set test limits. All the engineer had to do was load the configuration file into Notepad and make the necessary changes. This made the software very flexible to changing design requirements.

[Battery Sleep Mode]
Upper Voltage Limit (V) = "1"
Lower Voltage Limit (V) = "0.0"
Wait Time (s) = "2.000000"

Example of Configuration file test limits

A report print out was generated at the end of the test that indicated the results of the test. Data acquired from the test was saved as an xml file.

Result

Medical Device Battery test using SMBus software enabled the customer to quickly and easily test their battery. This freed up resources that previously had to test the product manually before this software was developed. The software was easy to operate by any user and the test engineer had easy access to the test limits to accommodate design changes. We also were able to use existing hardware saving the customer costly and time consuming calibration.

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