Optimize battery life for battery powered medical devices and wireless medical devices: Page 2 of 5

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).
and integrating the instrumentation and writing test programs. Instead, you can spend time analyzing more insightful results, giving you confidence to make design changes that lead to a more reliable and energy efficient BPMD.

The new approach uses a different instrument for measuring and analyzing your BPMD’s power consumption. A source measurement unit (SMU) is a standard instrument, available today, providing an ideal foundation for measuring power consumption. An SMU allows one to source a voltage/current and measure a current/voltage. Since the SMU knows what voltage it applies and the current that it measures, it is capable of making voltage, current, and power measurements without additional equipment. Assuming the SMU’s power rating is sufficient, it can also replace the power supply needed in the traditional method. Additionally, an SMU makes current measurements without the need for external shunt resistors.

Combining this measurement capability with a data-logger function allows the capture of voltage, current, and power over time. Not only can multiple operating states of the BPMD be obtained during the datalog record, the BPMD’s use of battery capacity (Ah) can also be calculated. Using an SMU based architecture significantly simplifies your setup to measure and analyze the power consumption of your BPMD. For our example, the world’s first Wi-Fi blood pressure monitor system ( blip) was characterized.

Figure 2  blip wireless blood pressure cycle:  1) Initial sleep mode, 2) Pressing ‘User 1’ button to measure blood pressure (BP), 3) Inflating BP cuff, 4) Measuring BP, 5) Passing information for Wi-Fi___33 communication, 6) Wi-Fi transmitting BP measurement information to internet, 7) Display of BP measurement, 8) Return to sleep mode. Markers are set to capture information within the complete measurement cycle. Peak current (during pump operation) was 619mA. Drain on battery capacity for one cycle is 2.37mAh.

A state-of-the-art SMU has recently been developed with an effective resolution of 28 bits when measuring current. This dynamic range allows measurement of

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