3B32 Isolated Input Module

FEATURES
Interfaces, amplifies, & filters a process-current input.
Process-current input signals are measured by reading the
voltage across an external precision 100Ω resistor (supplied
with module).
Module provides simultaneous precision voltage and
current outputs.
Module circuitry can withstand 220v rms at the input screwterminals.
All 3B32 series modules are mix-and-match and Hot
Swappable.

APPLICATIONS
Industrial signal conditioning
Industrial signal isolation
Industrial signal filtering



PRODUCT OVERVIEW
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
modules.

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.




GENERAL DESCRIPTION
The 3B32 is a single-channel signal conditioning module that
interfaces, amplifies and filters a process-current input and
provides simultaneous precision output voltage and current.
Process-current input signals are measured by reading the
voltage across an external precision 100Ω resistor (supplied).
Model 3B32 performs complete signal conditioning, including
isolating (+1500V peak input-to-output and power) and
protecting their computer side outputs from damage and loss of
signal integrity, and shielding their inputs from damage from
field-side over-voltage faults up to 220V rms. The current
output withstands 130V rms without damage and interfaces
user equipment through screw terminals located on the 3B
Series backplane. Each plug-in, mix-and-match, hot-swappable
module is easily field calibrated via front-panel zero and span
adjustments for both voltage and current outputs.

3B Series Custom-Ranging Program – Externallyprogrammable
Model 3B32-00, enables the user to configure a
special input range by using the optional plug-on AC1310
ranging card, which houses user-supplied 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 ranges.

A chopper-stabilized low-drift (+1uV/oC) input amplifier
assures long-term stability. At the amplifier input, a stable,
zero-scale input voltage is subtracted from the input signal to
set the zero-scale value. Zero suppression can exceed 100% of
the input range. This is ideal for expanded-scale applications
requiring high-resolution measurement of a selected portion of
an input signal. For user convenience, the zero and span can be
factory configured to meet custom range needs (Model 3B32-
CUSTOM) or can be externally programmed (Model 3B32-00)
via user supplied resistors inserted in the optional AC1310 plugon
ranging card. Internal low-pass filtering with a 3Hz cutoff (-
3dB) two-pole Butterworth filter enhances both 60 dB normalmode
and 160 dB common-mode rejection at 50/60 Hz,
enabling accurate measurement of small signals in high
electrical noise.

Signal isolation is accomplished by transformer coupling with a
proprietary modulation technique for linear, stable and reliable
performance. The differential input circuit on the field side is
fully floating, eliminating the need for any input grounding. A
demodulator on the computer side of the signal transformer
recovers the original signal, which is then filtered and buffered
and drives a voltage-to-current converter to provide the current
output.