The AESMART Model 302A is an economical alternative to the AESMART model 2000 for those who are primarily interested in Tribology, Head disk interference (HDI) measurements, metal cutting, grinding and leak detection.
The DECI AESMART 302A is a virtual instrument designed for Acoustic
Emission testing of structures and processes that produce high
density signals such as high pressure leaks and friction. In the
latter category such processes as Head Disk Interference (HDI),
metal cutting, grinding, and polishing all produce high density
AE signals suitable for analysis by the AESMART 302A.
The hardware portion of the instrument detects, amplifies and
splits into two frequency ranges the signals from an AE transducer
coupled to the part to be inspected. These amplified and filtered
signals along with the broadband signal and the Average Signal
Level (ASL) of the high and low frequency channel's are output
with BNC connectors on the front panel for observation with an
oscilloscope.
The ASL signals are output via a ribbon cable to a National Instruments
DAQ1200 PCM-CIA card. The ASL voltage of the high and low frequency
channels is sampled, and a HF/LF ratio of these voltages is calculated.
It is this ratio that is the primary factor used in analyzing
the various processes mentioned previously. For example the data
shown in the screen above shows the HF/LF ratio observed from
an aluminum plate that has been previously abraded with 180 and
600 grit sandpaper. A DECI SE900-MWB transducer coupled to the
plate with petroleum jelly detected AE signals created by quickly
rubbing with the index finger across the two abraded surfaces.
The HF/LF ratio plotted as a function of time clearly shows the
difference in roughness of the two surfaces. A report entitled
"Measurement of Surface Roughness by Acoustic Emission Techniques"
can be observed on our web page for those interested in more detail
concerning this technique.
HELP- The function of any of the features present on the
screen can be observed by first clicking on HELP and then moving
the cursor with a mouse to any feature present on the screen for
description of its function.
STARTING A TEST- Click on the arrow in the upper left-hand
corner of the screen.
EVENT BEEP-Clicking on this button will give an audible
sound for each valid event.
GRAPHICS- Clicking on "Save to Excel" button
will transfer all data to an excel spreadsheet. Be sure to open
excel first. An example of the data saved is shown below.
STOPPING A TEST- Click on the stop button. Do not stop
a test unless you are ready to start a new test. Once the program
stops starting a new test will cause all data to be lost unless
saved.
HOLD- Click on this button to prevent the system from acquiring
data. Sometimes it is necessary to interrupt a test to change
a transducer etc. This will prevent extraneous noise data from
being recorded while making changes. Clicking on hold again will
cause the system to continue recording data for the same test.
SAMPLE RATE-This window shows the sample rate of the A/D
in milliseconds. It can be changed with the up-down arrows or
by selecting the window contents and typing in new values.
EVENTS AVERAGED- This window selects the number of events
to average when the windowed average of the ratios is selected
for a plot parameter.
RUN TIME- the total run time for a test in seconds is shown
in this window.
AMPLITUDE DISPLAY- this window allows selection of several
parameters to be plotted as a function of time they are:
It is recommended to start each test with the average ratio or
HF/LF ratio as the plot parameter. If the test is started with
HF voltage or LF voltage the data will not appear on the screen.
The data has been recorded and can be observed by first going
to the ratio selection and then selecting HF or LF voltage
DEFAULT THRESHOLD- The switch in the "enable"
position tells the A/D what minimum voltage threshold in the window
below to sample. It is recommended to always operate with this
switch enabled
RATIO FILTER- When this switch is in the "enable"
position, HF/LF ratios will be required to exceed the value in
the ratio threshold window in order to be considered a valid event
and be recorded in the data base
HF/LF RATIO- The left portion of this window shows the
last ratio calculated during a test. The ratio threshold window
is used to set the minimum ratio considered by the ratio filter
as a valid event.
VOLTS mvPEAK- This window shows the HF and LF voltages
recorded for the latest event in millivolts
EVENT COUNT-This window shows the total number of valid
events received during a test. The summation of these events is
one of the real time plot parameters
REAL TIME PLOTS-The Y-axis of the screen graphics is selected
by the amplitude display arrows as stated previously. Both the
X and Y axis scales can be changed by selecting the maximum range
value and typing in a new value and pressing ENTER.
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