Optimize battery life for battery powered medical devices and wireless medical devices

October 21, 2013 //By Mike Hawes
Optimize battery life for battery powered medical devices and wireless medical devices
Mike Hawes explains how the medical device industry is seeing an explosion in the number and type of mobile and wireless medical devices, and is ripe for a new approach to analyzing the energy requirements of your battery powered medical devices (BPMDs).

Traditional method and test challenges

The common method to analyze the energy requirements of your BPMD is for the design engineer to assemble multiple instruments and miscellaneous external circuitry. Typically a scope, DMM, or digitizer is used for making measurements (usually two channels, one to measure voltage and the other current), a power supply and/or battery to power the medical device, and some shunt resistors for current measurements. A method to control the medical device (to test its different states of operation) as well as control the instrumentation to collect and analyze the desired data (current, voltage, power) will need to be developed. This can be manual, or semi-automated, by connecting the instruments to a computer and writing software to programmatically control the test. The result is typically multiple files with voltage and current waveforms for the different operating states of the device. It is left up to the designer to manipulate the data to determine power consumption for each of the operating states of the BPMD.

Figure 1  Traditional setup for measuring sleep current

The information available from this approach is limited. Because of the finite dynamic range of scopes, digitizers, and most DMMs (8-21 bits), different shunt resistors are required to measure the peak values (100mA to Amps) and the sleep current values (low microamps). What is missed is the critical understanding of the transient behavior from sleep mode to peak demand of your design. Additionally, many of the larger energy demands of the BPMD are dynamic and more challenging to characterize. In summary, this simple power consumption information doesn’t provide much insight into how you would change your BPMD design to improve reliability and optimize battery life.

An integrated solution

The value of an integrated solution goes beyond saving the time and cost of integrating your own system. With a solution focused on the test challenges mentioned above, you are removed from low value-added tasks like gathering

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