Design of a Computer Controlled Test System for

1. Design of a Computer Controlled Test System for Micro-Electro-Mechanical-Resonator (MEMR) Based Gas Sensor Presenter: Joshua Ward Co-Author: Robert MacKinnon Advisor: Prof. Mustafa Guvench Electrical Engineering Department – University of Southern Maine HP 54504A Digital Oscilloscope Computer, running MEMR Controlled Environment LabView software HP 5335A Universal Counter HP 4194A Impedance/Gain Analyzer GPIB MFC Quartz Crystal Monitor Gas Out Gas Gas In Programmable Power supply Computer controlled Mass Flow Controller Unit The goals of this project are to design and develop a computer-controlled test system to measure and characterize the response of a MEMR device to various gas mixtures and concentrations. The resonance frequency of this MEMR device is determined by: ω = 1/(2π) * √k/m Which is the inverse of the product of its vibrating mass and its spring constant. The MEMR device will be coated with a thin film of a polymer with gas absorption properties. As a detectable gas is passed over the device its resonant frequency response will be noted. The MEMR device will respond to the presence and concentration of the gas to be sensed with a decrease in its resonance frequency. The computer software being used as the platform for this computer controlled test system is LabView, by National Instruments. This program is being used for interfacing, communicating, data acquisition and control between a personal computer and the measurement setup via GPIB bus and serial ports. It is a graphical programming language that uses icons instead of lines of text to create applications. The Test Setup: The gas or vapor to be sensed will be mixed with an inert carrier gas to adjust its concentration. The flow rates and concentration levels are being determined using computer controlled mass flow controllers. The LabView program being written will control the injection time and the mixing ratio of the gas along with temperature control within the test chamber. After each injection of gas, the program will trigger all measurement instruments and gather data to quantify and generate plots of sensor response vs. injected gas concentration and temperature. We will be using a Sycon Quartz Crystal Monitor as a reference. This device also monitors the frequency shift as a substance is deposited onto it. Measurement Equipment used: HP 54504A Digital Oscilloscope HP 5335A Universal Counter HP 4194A Spectrum Analyzer KI 213 Programmable Source STM-1 Sycon Quartz Crystal Monitor This is the LabView front page, or user control panel, for the Sycon Quartz Crystal Monitor. This measures the rate of deposition and thickness of the deposited film. A similar program will be written for the MEMR device. The MEMR device to be tested. The Test Set-Up