Dytran 3055D Series, 3055D1, 3055D2, 3055D3, 3055D4 Operating Manual

Dynamic Transducers and Systems

21592 Marilla St. • Chatsworth, CA 91311 • Phone [phone]
www.dytran.com • e-mail: [e-mail]

OG3055D.docx
Rev A ECN 10060 06/21/13
Rev B ECN 11394 11/04/14
Rev C ECN 12135 07/27/15

OPERATING GUIDE

SERIES 3055D

IEPE ACCELEROMETERS, 10, 20, 50, 100, 200 & 500 mV/g

HERMETICALLY SEALED AND BASE ISOLATED

NOTE:

Series 3055D features hermetically sealed construction and
electrically isolated base for "off-ground" performance.
Hermeticity is obtained by all-welded construction and
glass-to-metal sealed connector. Case material is titanium.
Base ground isolation is by an electrically isolated threaded
insert located in the base of the instrument. Signal ground
return is electrically isolated from the mounting surface.

This guide contains:

1) Operating instructions, Series 3055D.

2) Outline/installation drawing, Series 3055D

3) Specifications, Series 3055D

NOTE: IEPE is an acronym for Integrated Electronics Piezoelectric types of low impedance voltage mode sen so rs with
built-in amplifiers operating from constant current sources over two wires. IEPE instruments are compatible with other
comparable systems labeled LIVM™

1

OPERATING INSTRUCTIONS MODEL SERIES 3055D

IEPE ACCELEROMETERS

INTRODUCTION

The Dytran Model Series 3055D consists of
six accelerometers, differing only in sensitivity and
range. Model 3055D1 is 10 mV/g, Model 3035D2 is
100 mV/g, Model 3055D3 is 500 mV/g, Model 3055D4
is 50 mV/g, Model 3055D5 is 20mV/g, and Model
3055D6 is 200mV/g

These accelerometers features Integrated
Electronics Piezoelectric (IEPE) operation. The self­generating seismic element, utilizing piezoceramic
crystals in planar shear mode, convert acceleration to
an analogous electrostatic charge mode signal. This
very high impedance signal is fed to the input of a
miniature on-board IC JFET charge amplifier that
drops the output impedance level ten orders of
magnitude, allowing this instrument to drive long
cables without an appreciable effect on sensitivity and
frequency response.

Simple constant current type power units
supply power to operate the integral charge amplifier
and separate the signal from the DC bias at the output
of the internal amplifier. Coaxial cables or even twisted
pair wire may be used to connect accelerometer to
power units. Power and signal are conducted over the
same two-wire cable.

Model series 3055D also features signal
ground isolation from the mounting surface to avoid
annoying ground loops and hermetic sealing for
normal operation in moist and dirty environments.

DESCRIPTION

Figure 1, below, is a representative cross
section of series 3055D.

PIEZOCERAMIC CRYSTAL

SEISMIC MASS

10-32 CONNECTOR,
AMPLIFIER IS LOCATED IN
CAVITY BEHIND
CONNECTOR

Figure 1-Cross section, series 3055D

The seismic masses, made from a very dense
tungsten alloy, are tightly preloaded against the
ceramic crystals by means of a special preload screw,
under hundreds of pounds of force. This is so there is
absolutely no relative motion between mass, crystals
and base, thus keeping the non-linearity low and the
natural frequency high.

The force from acceleration (vibration or
shock) acting upon the mounting base is transferred to
the seismic masses through the crystals, stressing the
crystals in shear and producing an electrostatic charge
signal analogous to the input acceleration. This charge
is impressed across the input of the JFET IC charge
amplifier.

Because the IC is a 2-wire IEPE charge
amplifier, the dynamic output voltage signal is
impressed across the connector of the sensor which is
the same point into which the constant current from
the power unit is applied. (See Figure 2 below)

Figure 2-Electro-mechanical schematic,
accelerometer and power unit system.

When constant current from the IEPE power
unit is applied to the accelerometer amplifier input
terminal, the amplifier "turns on" at approx. +10 Volts
DC quiescent bias level. When the accelerometer
senses acceleration, the resultant signal is
superimposed upon this bias voltage.

In the power unit, in its simplest form, a
capacitor blocks the DC bias and allows the dynamic
signal voltage to be separated and brought out to an
"output" jack on the power unit. At this point the signal
may be connected directly to almost any type of
readout instrument such as DVM's, oscilloscopes, data
collectors, spectrum analyzers, etc. The approximate
100 Ohm output impedance of the signal allows the
driving of long cables without adverse effects on
sensitivity or frequency response.

2