Gas Pressure Meter Advisor: Naomi Chesler Client: EWH Team Members Ksenija Bujanovic – Team Leader Claire Edlebeck – Communicator Mike Oldenburg – BWIG Chris Webster - BSAC

Background Information Engineering World Health (EWH) project Current Technology Pressure meters Anesthesia and ventilator machines Device need in Third World Countries merDirect/images/catalog/730012_150.jpg

Design Constraints Cost less than $5 in quantities of 500 Test a variety of gasses Measure pressures 0 – 80mmHg Have a digital readout Be accurate to within 10% of true value Be reusable

Past Work - Circuit Converts pressure into voltage Wheatstone bridge Potentiometers enable circuit calibration Connects to microcontroller Displays values on 7- segment LED Powered by 9V batteries

Past Work – Device Connection Connect pressure sensor to ventilator using T-connector

Current Work Transfer from breadboard to PCB. Addition of low power op amps Peak vs. continuous pressure reading Calibration

Previous Testing Last semester Pressure to voltage relationship Different gas compositions Sensitivity

Future Testing Accuracy With new display, various gas compositions at hospital using O 2, medical air, and CO 2 comparing input pressure and LED reading Correlation with digital readout after calibration with both anesthesia and ventilation machines Various environments (20 – 100% humidity, ºF) to ensure adequate accuracy under all condition

Future Testing II Safety Frequency of calibration required by measuring drift of one iteration of circuit every day Ease of calibration by observing time required to calibrate by various users Battery life by testing over extended period of time using same battery

Calibration Syringe readily available Create and label desired pressures with syringe and monometer Connect syringe to pressure meter and adjust potentiometers

Budget - Comparison Pressure Meter KAL 84 Electronic Pressure Calibrator Research Blood Pressure Transducer EWH Gas Pressure Meter Device Price ($) 1, , Picture LED YES Meets Accuracy Requirement YES Number of Qdoba burritos ($7)

References Harvard Apparatus. Superior Products for Physiology, Pharmacology & Toxicology. 2008/09. Harvard Bioscience Company. J. G. Webster (ed.). Bioinstrumentation John Wiley & Sons. Duke Univerisity. "Engineering World Health." 2007.

Questions?