Transcript Slide 1

Design of a Computer Controlled Test System for
Micro-Electro-Mechanical-Resonator (MEMR) Based Gas Sensor
Presenter:
Joshua Ward
Robert MacKinnon Advisor: Prof. Mustafa Guvench
Electrical Engineering Department
Co-Author:
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.
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
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.
HP 54504A Digital Oscilloscope
Computer, running
LabView software
HP 5335A Universal
Counter
GPIB
MEMR
Controlled
Environment
HP 4194A Impedance/Gain
Analyzer
Gas Out
+
Quartz Crystal Monitor
Carrier Gas
MFC +
The MEMR device to be tested.
Gas
Programmable
Power supply
Gas
In
Computer controlled
Mass Flow Controller Unit
The Test Set-Up
Gas
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.