ANALOG DEVICES 3B18 Service Manual

Wide Bandwidth Strain Gage Input

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FEATURES

Wideband (20 kHz) single-channel signal conditioning
module.

Module Bandwidth is user-selectable between 20 kHz and
100Hz, with user-supplied filter caps installed in the optional
AC1310 ranging card.

Interfaces, amplifies, and filters signals from balanced 4-arm
full-bridge strain-gage bridges.

Module provides simultaneous precision voltage and
current outputs.

Module circuitry can withstand 130v rms at the input screw­terminals

All 3B18 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).

3B18

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 3B18 Functional Block Diagram

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 +
modules), and feature two high-level analog outputs that are
compatible with most process instrumentation. The isolated
input modules also provide +

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.

0.1%, low drift of +1 uV/oC (low-level input

1500 V peak isolation.

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

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GENERAL DESCRIPTION

The 3B18 is a wideband (20kHz) single-channel signal
conditioning module which interfaces, amplifies, and filters
signals from balanced 4-arm full-bridge strain-gage bridges
with a resistance from 100Ω to 10 kΩ, providing simult aneous
precision voltage and current outputs. The module provides two
user-selectable (via front-panel switches) bridge excitation
voltages: +10 V for bridges with a load impedance down to
300W or +3.33V for 120W bridges or others below 300W.
Module bandwidth is also user-selectable between 20 kHz and
100 Hz, with user-supplied filter capacitors installed in the
optional AC1310 ranging card. The 3B18 protects the computer
side from damage due to field-side over-voltage faults up to
130V rms. In addition, the current output withstands 130V rms
without damage and interfaces user equipment through screw
terminals located on the 3B Series backplane. The 3B18 is a
plug-in, mix-and-match, hot-swappable module which is easily
field calibrated via front-panel zero and span adjustments for

.

3B18

both voltage and current outputs.

3B Series Custom-Ranging Program – Externally­programmable Model 3B18-00, 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 (+
assures long-term stability. For user convenience, the zero and
span can be factory configured to meet custom range needs
(Model 3B18-CUSTOM) or can be externally programmed
(Model 3B18-00) via user supplied resistors inserted in the
optional AC1310 plug-on ranging card.

1uV/oC) input amplifier

Figure 2

.

Rev. 0 | Page 2 of 8

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3B18 Models Available

Model Input

3B18-00 Full

3B18-01 Full

3B18-02 Full

3B18-Custom Full Bridge * +10.0 V or +3.33 V * *

1

Output current range may be user programmed to 4 mA to 20 mA using jumper supplied.

2

Requires AC1310 ranging card.

* Custom Input/Output ranges are available. Refer to configuration guide.

Bridge

Bridge

Bridge

Bridge

3B18 Specifications
(typical @ +25°C and ±15 V dc, and +24 V dc Power)

Description Model 3B18

Standard Range ±30 mV (3 mV/V sensitivity @ V

Custom Ranges ±5 mV to ±500

Voltage (RL > 2 KΩ)

Current (RL = 0 to 850Ω)1

Maximum Current Output Span 0 mA to 31 mA

Initial @ +25°C ±0.1% Span

Nonlinearity2 ±0.01% Span

Voltage Output

Zero ±3 µV/°C (RTI)

Span ±25 ppm of Reading/°C

Current Output3

Zero ±25 ppm of Span/°C

Span ±25 ppm of Reading/°C

Input

Range

Externally

Programmable

-30 mV to +30 mV +10.0 V or +3.33 V 3 mV/V @ 10 Vexc -10 V to +10 V &

-10 mV to +10 mV +10.0 V or +3.33 V 3 mV/V @ 3.33 Vexc -10 V to +10 V &

3

Excitation1 Sensitivity Output

+10.0 V or +3.33 V Externally

Input Range

±10 mV (3 mV/V sensitivity @ V

Output Range

-10 V to +10 V

4 mA to 20 mA or 0 mA to 20 mA

Accuracy2

Stability vs. Temperature

Programmable3

= +10V)

exc

= +3.33 V)

exc

Ranges

-10 V to +10 V &
0 mA to 20 mA

0 mA to 20 mA

0 mA to 20 mA

3B18

Bridge Excitation

Voltage user-selectable +10 V or +3.33 V

Voltage, tolerance ±2%

Voltage vs. Temperature ±0.0015%/°C

Bridge Resistance Range

V

= +10.0 V

exc

300 Ωto 1 kΩ

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