20 July 2009

3B20 Module (AC Strain Gage, Torque Transducer Input)

Interfaces, amplifies, & filters signals from 4-arm AC bridge
transducer signals ranging between 1.5mV rms & 150mV
Module provides an AC excitation voltage of 2V rms to 10V
rms at frequencies between 1kHz & 10kHz..
Module provides simultaneous precision voltage and
current outputs.
Module circuitry can withstand 130v rms at its current
output terminals without damage.
All 3B20 series modules are mix-and-match and Hot

Industrial signal conditioning
Industrial signal isolation
Industrial signal filtering

The 3B Series of Signal Conditioning I/o Subsystems provide a
low-cost, versatile method of transferring analog transducer
signals to a data acquisition, monitoring or control system
without the inherent noise, non-linearity, drift and extraneous
voltages. The modules are designed to directly accept analog
signals from Thermocouples, RTD’s, AC and DC Strain Gages,
Torque Transducers, Frequency Transducers, LVDTs, millivolt
or process current signals. The modules amplify, isolate,
linearize and convert the transducer output signals to
standardized analog inputs for high-level analog I/O
subsystems. The 3B Series Subsystem consists of a 10” relay
rack with universal mounting backplane and a family of plug-in
(up to 16 per rack) input and output signal conditioning

Eight and four channel backplanes are also available. Each
backplane incorporates screw terminals for sensor inputs and
current outputs and a 26-pin connector for high-level singleended
voltage outputs to the user’s equipment.

The input modules feature complete signal conditioning
circuitry optimized for specific sensors or analog signals and
provide two simultaneous high-level analog outputs: 0 to +10V
(or +10V) and 4-20 mA (or 0-20 mA).

Output modules accept 0 to +10V (or +10V) single-ended
signals and provide an isolated 4-20 mA (or 0-20 mA) process
signal. All modules feature a universal pin-out and may be
readily hot-swapped under full power and interchanged without
disrupting field wiring.

The Analog Devices 3B Series Signal Conditioning Subsystem is
designed to easily handle signal conditioning problems in
measurement and control applications. Some typical uses are in
microcomputer-based data acquisition systems, programmable
controllers, analog recorders, dedicated control systems, and any
other applications where monitoring of temperature, pressure,
flow and analog signals are required. Since each input module
features two simultaneous outputs, the voltage output can be
used to provide an input to a microprocessor-based data
acquisition or control system while the current output can be
used for analog transmission, operator interface, or an analog
backup system.

Each input module is a single-channel signal conditioner which
plugs into a socket on the backplane and accepts its signal from
the input screw terminals. All input modules provide input
protection, amplification and filtering of the input signal,
accuracy of +0.1%, low drift of +1 uV/oC (low-level input
modules), and feature two high-level analog outputs that are
compatible with most process instrumentation. The isolated
input modules also provide +1500 V peak isolation.

The choice of a specific 3B module depends upon the type of
input signal. Input modules are available to accept millivolt, volt,
process current, thermocouple, RTD, AC and DC strain gage,
frequency and LVDT inputs. The voltage output of each module
is available from the system I/O connector while the current
output is available on the output screw terminals.

The 3B20 is a wideband single-channel signal-conditioning
module which interfaces 4-arm AC bridge transducer signals
ranging between 1.5mV rms and 150mV rms, providing
simultaneous precision voltage and current outputs. In addition,
the module provides an AC excitation voltage of 2V rms to 10V
rms at frequencies between 1kHz and 10kHz. The module
withstands 130V rms at its current output terminals without
damage thereby shielding computer-side circuitry from fieldside
over-voltage conditions. The 3B20 is a plug-in, mix-andmatch,
hot-swappable module and is easily field calibrated via
front-panel zero and span adjustments for both voltage and
current outputs.

3B Series Custom-Ranging Program – Externallyprogrammable
Model 3B20-00, enables the user to configure a
special input range, including tare weight suppression, by using
the optional plug-on AC1310 ranging card, which houses usersupplied
resistors to determine zero and span. To facilitate
selecting resistors, a Windows program, 3B-CUSTOM,
calculates resistor values based on the user-desired input/output

The 3B20 input and AC bridge excitation output terminals are
protected for up to 130V rms. The excitation amplitude and
frequency can be specified with the Model 3B20 CUSTOM or
user configured with Model 3B20-00 and an optional plug-on
Model AC1310 ranging card. Both the voltage and current
outputs can be independently adjusted for a minimum of +1V
for the zero and 25% of the span range with front-panel useraccessible
potentiometers. In addition, phase shifts of up to
37.25o between excitation signal and the output signal from the
strain gauge or torque transducer can be compensated via frontpanel
screw terminal adjustments.