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
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 ? 1/(2p)
vk/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