ANALOG DEVICES 3B34 Service Manual
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Isolated, Linearized RTD Input
FEATURES
Isolates, amplifies, linearizes, & protects analog input
voltages from a wide variety of two-, three- and four-wire
Resistor Temperature Detectors (RTDs).
Module provides a constant +10V bridge excitation voltage.
Module provides simultaneous precision voltage and
current outputs linear to input temperature.
RTD excitation current and three-wire lead resistance
compensation provide a complete signal conditioning
solution.
Module circuitry can withstand 220v rms at the input screwterminals.
All 3B34 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).
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.
FUNCTIONAL BLOCK DIAGRAM
Figure 1. 3B34 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 sysem I/O connector while the current
output is available on the output screw terminals.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
0.1%, low drift of +1 uV/oC (low-level input
1500 V peak isolation.
www.analog.com
3B34
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GENERAL DESCRIPTION
The 3B34 is a single-channel signal conditioning module which
amplifies, protects, filters, linearizes, and isolates analog input
voltages from a wide variety of two-, three-, and four-wire
Resistor Temperature Detectors (RTDs), providing
simultaneous precision voltage and current outputs, linear to
input temperature. RTD excitation current and three-wire lead
resistance compensation provide a complete signal conditioning
solution. The 3B34 protects its computer side outputs from
damage and loss of signal integrity by isolating them up to
+1500V peak and shielding its input and excitation circuit from
damage from field-side over-voltage faults up to 220V rms. The
current output withstands 130V rms without damage and
interfaces to user equipment through screw terminals on the 3B
Series backplane. The 3B34 is a plug-in, mix-and-match, hotswappable module, easily field calibrated via front-panel zero
and span adjustments for both voltage and current outputs.
3B Series Custom-Ranging Program – Externallyprogrammable Model 3B34-00, 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.
3B34
A differential chopper-stabilized low-drift input amplifier
provides stable gain and long-term stability. This enables the use
of very low RTD excitation current to minimize self-heating
and preserve measurement accuracy. A 250 uA excitation
current for platinum and nickel RTDs and a 1mA excitation
current for copper RTDs is provided to create an input voltage
to the 3B34. For three-wire RTDs, the excitation current flows
through the third RTD lead to eliminate the effect of lead
resistance with an accuracy of +0.02oC/W. Internal multi-pole
low-pass filtering with a 3-Hz cutoff (-3dB) enhances normalmode and common-mode ejection at 50/60 Hz, enabling
accurate measurement of small signals in high electrical noise.
The differential input circuit on the field side is fully floating,
eliminating the need for any input grounding. Signal isolation is
accomplished by transformer coupling using a proprietary
modulation technique for linear, stable and reliable
performance. A demodulator on the computer side of the signal
transformer recovers the original signal, which is then filtered
and buffered to provide a low-noise, low-impedance output
voltage; this output also drives a voltage-to-current converter to
provide a simultaneous current output for interfacing versatility.
.
Figure 2
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Rev. 0 | Page 2 of 8
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3B34 Models Available
Model RTD Sensor
3B34-00
3B34-01
3B34-02
3B34-03
3B34-04
3B34-Custom
Model RTD Sensor (2 or 3-wire) Input Range Output Ranges1
3B34-C-00
3B34-C-01
3B34-C-02
3B34-Custom
Model RTD Sensor
3B34-N-00
3B34-N-01
3B34-Custom
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.
(2,3, or 4-wire)
100 Ω Pt, (alpha) = 0.00385
100 Ω Pt, (alpha) = 0.00385
100 Ω Pt, (alpha) = 0.00385
100 Ω Pt, (alpha) = 0.00385
100 Ω Pt, (alpha) = 0.00385
100 Ω Pt, (alpha) = 0.00385
10 Ω Copper, (alpha) = 0.004274
10 Ω Copper, (alpha) = 0.004274 0°C to +120°C (10Ω @ 0°C)
10 Ω Copper, (alpha) = 0.004274 0°C to +120°C (10Ω @ +25°C)
10 ΩCopper, (alpha) = 0.004274
(2,3, or 4-wire)
120 ΩNickel, (alpha) = 0.00672
120 Ω Nickel, (alpha) = 0.00672
120 Ω Nickel, (alpha) = 0.00672
Externally Programmable 2 0 V to +10 V & 0 mA to 20 mA
Externally Programmable 2 0 V to +10 V & 0 mA to 20 mA
Externally Programmable 2 0 V to +10 V & 0 mA to 20 mA
3B34
Input Range Output Ranges1
-100°C to +100°C 0 V to +10 V & 0 mA to 20 mA
0°C to +100°C 0 V to +10 V & 0 mA to 20 mA
0°C to +200°C 0 V to +10 V & 0 mA to 20 mA
0°C to +600°C 0 V to +10 V & 0 mA to 20 mA
* *
0 V to +10 V & 0 mA to 20 mA
0 V to +10 V & 0 mA to 20 mA
* *
Input Range Output Ranges1
0°C to +300°C 0 V to +10 V & 0 mA to 20 mA
* *
3B34 Specifications
(typical @ +25°C and ±15 V dc, and +24 V dc Power)
Description Model 3B34
Input Ranges
Standard Ranges Refer to Model Table
Custom Ranges
Voltage
Current
Maximum Current Output Span 0 mA to 31 mA
Initial @ +25°C ±0.1% Span
Nonlinearity3 ±0.05% Span
-200°C to +850°C (100Ω Platinum; 2-, 3- or 4-wire)
-80°C to +350°C (120Ω Nickel; 2-, 3- or 4-wire)
-100°C to +260°C (10Ω Copper; 2- or 3-wire)
Output Ranges
0 V to +10 V (R
4 mA to 20 mA or 0 mA to 20 mA (R
Accuracy
Stability vs. Temperature
L
2
> 2 kΩ)
= 0 to 850Ω)1
L
Rev. 0 | Page 3 of 8
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