Dytran 3224C User manual

Dynamic Transducers and Systems
21592 Marilla St. • Chatsworth, CA 91311 • Phone [phone]
www.dytran.com • e-mail: [email protected]
OG3224C.DOC
REV A 12-5-11, ECN8132
REV B ECN 10349 09/09/13
REV C ECN 10389 09/24/13
OPERATING GUIDE MODEL 3224C
MINIATURE PIEZOELECTRIC CHARGE MODE ACCELEROMETER
This manual contains:
1) Specifications, model 3224C
2) Outline/Installation drawing 127-3224C
3) Operating instructions Model 3224C

REV C ECN 10389 09/24/13
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OPERATING INSTRUCTIONS
MODEL 3224C MINIATURE CHARGE MODE ACCELEROMETER
INTRODUCTION
Model 3224C is arguably, the world’s smallest
piezoelectric, charge mode piezoelectric designed to
mount in spaces inaccessible to other types of
accelerometers.
Featuring a titanium case and weighing only
0.2 grams, this instrument is ideal for the
measurement of shock and vibration of very small,
lightweight specimens such as printed circuit boards
and board-mounted components.
Designed for adhesive mount, Model 3224C
may be mounted in very narrow spaces only slightly
greater than .138 inch (3.51 mm).
A 3 ft. long coaxial cable is permanently
attached to the body of the accelerometer and
terminates in a 10-32 coaxial male-threaded
connector.
DESCRIPTION
Refer to outline/installation drawing 127-
3224C.
Model 3224C is constructed in "teardrop" form
with the connector at the end of the teardrop. The
body is made from titanium for low mass and high
stiffness.
Model 3224C generates an electrostatic
charge mode signal by stressing two " shear" type self-
generating piezoceramic crystals in response to input
acceleration. The crystal is preloaded to a flat crystal
support and is preloaded to this post by screws.
Because of its very low mass and high crystal
stiffness, this instrument has a resonant frequency of
about 40 kHz. This means that it may be used to
measure high frequency vibrations with very little error.
INSTALLATION
IMPORTANT: Before mounting the Model
3224C, it is important to identify the mounting surface.
It is the raised .129 diameter boss at the bottom of the
instrument. The flat side is the top of the instrument.
DO NOT MOUNT TO THE TOP SURFACE. Not only
will the signal polarity be reversed and the sensitivity
and frequency response be adversely affected but
there is danger of damaging the top cap of the
accelerometer when removing it, if mounted in the
inverted position. This type of damage is considered
abuse and is not covered by the manufacturer's
warranty.
To install Model 3224C, it is necessary to
select (or prepare) a flat surface to accept the .129
diameter mounting surface of the instrument. As a rule
of thumb, the flatter the mounting surface, the better
the high frequency response will be. A surface flat to
.001 TIR will give excellent results when a thin glue
line is used during mounting.
Clean the mounting surfaces with solvents
such as alcohol or Freon, etc., to remove debris, oils
and greases before mounting.
The recommended adhesives are the "instant"
setting cynoacrylate cements such as Eastman 910
and "Crazy Glue". Apply a very small drop to either
mating surface, and simply press the 3224C to the
mating surface with the finger and hold for 30 seconds.
If the adhesive does not set, check the expiration date
on the container. It is our experience that when the
glue gets old, the first indication is that it will not set up
properly. Replace if necessary.
Other types of adhesive may be used but
consider them carefully. Dental cement is not
recommended for this instrument because if its
tenacity. Removal when this adhesive is used may
harm the instrument.
In some cases, mounting waxes such as
"Petro" wax may be used to mount the 3224C but this
method is not suitable for measurements at high
temperature and high frequency.
Irrespective of which adhesive is used, keep
the glue line thin, i.e., don't use too much adhesive.
Too much adhesive places a "spring" between the
specimen and the instrument. This can create another
second order spring mass system (the mass being the
weight of the accelerometer) and can cause serious
measurement errors at high frequencies.

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OPERATION
To operate Model 3224C, it is necessary to
use an electrostatic charge amplifier to convert the
charge mode output signal from the accel. to a low
impedance voltage mode signal which may then be
fed directly to the readout instrument(s).
A recommended charge amplifier for field use
is the Dytran Series 4751B. These instruments convert
the 3224C to Low Impedance Voltage Mode (LIVM)
operation. They are mounted in-line between the
3224C and the LIVM power unit and convert the pC/G
signal to mV/G. These miniature charge amplifiers are
available in four models with fixed sensitivities of 50,
20, 10 and 1 mV/pC. This yields nominal system
sensitivities of 30, 30, 12 and 0.6 mV/G, respectively.
For laboratory use, 3224C may be used with
any vibration type laboratory charge amplifiers and
even with most electrostatic types. Consult the factory
if there is a question about compatibility with available
charge amplifiers.
The cable supplied with Model 3224C is
terminated in a jack type (male thread) 10-32 coaxial
connector. The recommended extension cables are
the Dytran low noise coaxial cables, model 6013AXX
(10-32 plug to 10-32 plug) or the model 6053 (10-32
plug to BNC plug). Both cables mate directly with the
cable attached the 3224C. Other cables are available
if either of these does not meet your requirements.
Contact the Dytran sales department for help in
selecting the best cable for your requirement.
The polarity convention of Model 3224C is
negative charge output for acceleration toward the top
of the unit. This is so because most charge amplifiers
are inverting amplifiers, hence the resultant system
signal will be positive with the above input convention.
UNMOUNTING THE ACCELEROMETER
In order to "unmount" the Model 3224C, use
the Model 6725 tool. The larger slotted end of the tool
is used for this purpose. Slip the tool over the
accelerometer body from the rounded end and gently
rotate the tool in either direction until the adhesive
shears and the instrument is released.
Do not use pliers, wrenches and other tools to
remove the instrument, as these are certain to mar or
otherwise damage the unit.
MAINTENANCE AND REPAIR
The only maintenance necessary is to keep
cables and connections clean and free from moisture.
All charge mode systems are considered high
impedance systems and as such are susceptible to
moisture which degrades insulation resistance.
Should a problem arise with the accelerometer
or cable, contact the factory for assistance in trouble
shooting or returning the instrument for evaluation
and/or repair. Do not send the instrument back without
first calling the factory to obtain a Returned Material
Authorization (RMA) number.