Analog Devices B34 0 (3) Datasheet

Isolated, Linearized RTD Input

FEATURES

Amplifies, Protects, Filters, and interfaces input voltages
from a wide variety of two and three-wire platinum, copper
and nickel Resistor Temperature Detectors (RTDs).

Module provides a precision output of either +1 V to +5 V or
0 V to +10 V, linear with temperature.

All 7B34 series modules are mix-and-match and Hot
Swappable.

APPLICATIONS

Industrial signal conditioning
Industrial signal amplification
Industrial signal filtering

PRODUCT OVERVIEW

The 7B Series of signal conditioners feature small size, low cost
and a wide output voltage range for a variety of applications
including process control and factory-floor environments. The
single-channel 7B modules accept inputs from a range of
transducers and are fully rated over the extended -40

o

C industrial temperature range. All 7B Series modules are

+85
rated for a nominal power supply input of +24 VDC; and, for
maximum flexibility, they will accept supply voltages in the +14
VDC to +35 VDC range. The input modules, with the exception
of the 7B21, provide a high-level output voltage that is factory
configured for either the +1 V to +5 V or 0 V to +10 V range.
The 7B21 is a unity gain, isolated input module with an
input/output range of +10V. Output modules are available that
provide either isolated process current or isolated bipolar
voltage output. Model 7B39 converts either a +1 V to +5 V input
to a 4 to 20 mA output or a 0 V to +10 V input to a 0-20 mA
output. The input/output ranges of the 7B39 are factory
configured. The 7B22 is a unity gain module that provides an
isolated +10V output signal. All modules have a universal pin­out and may be readily hot-swapped under full power without
disrupting field wiring. Each module accepts analog transducer
signals and transfers them to a process control or factory data
collection system without the inherent noise, non-linearity, drift
and extraneous voltages which frequently accompany the
signals.

o

C to

7B34

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 7B34 Functional Block Diagram

The modules feature a maximum nonlinearity of +0.02% and
are factory calibrated to guarantee a maximum accuracy
specification of +

The 7B Series offers up to 1500 V rms continuous common
mode voltage isolation and 120 V rms of field wiring input
protection. The power supplies necessary to drive each of the
individual module’s input circuitry are internally isolated,
enabling the 7B Series modules to offer true channel-to-channel
isolation of the input signals.

The modules directly accept analog signals from
thermocouples, RTDs, current loop powered transmitters, and
other process control signals. The 7B Series modules amplify,
linearize, isolate, protect and convert the transducer output
signals to standardized analog inputs for high-level analog I/O
subsystems. The 7B Series Subsystem consists of 19-inch rack­compatible hardware (model AC 1363), with universal
mounting backplane and a family of plug-in (up to 16 per
backplane) input and output signal conditioning modules. Four­, eight-, and sixteen-channel backplanes are available. Each
backplane incorporates screw terminals for easy power
connections and field wiring, and includes a 25-pin D-type
connector for interfacing the high-level single-ended voltage
outputs to the user’s equipment. Gold-plated sockets are
provided on each channel of the backplane to ensure the
reliability of each module’s electrical connection.

0.1%.

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
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registered trademarks are the property of their respective companies.

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Tel: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

GENERAL DESCRIPTION

The 7B34 is a single-channel signal conditioning module that
interfaces, amplifies and filters input voltages from a wide
variety of two- and three-wire platinum, copper and nickel
Resistor Temperature Detectors (RTDs) and provides a
protected precision output of either +1 V to +5 V or 0 V to +10
V, linear with RTD temperature. Three-wire lead resistance
compensation is provided and 2- or 3-wire RTDs may be used.
RTD excitation current, and a predictable upscale open circuit
indication provide a complete signal conditioning solution.
Model 7B34 features a nonlinearity of +
RTDs). To accurately measure low level signals in electrically
noisy environments, 1500 V rms of galvanic transformer-based
isolation with a common mode rejection (CMR) of 160 dB @
50/60 Hz and a normal model rejection (NMR) of 60 dB @
50/60 Hz are provided. Rated to operate with a nominal +24
VDC supply, Model 7B34 is mix-and-match and hot-swappable
with other 7B Series input modules, so it can be inserted or
removed from any socket in the same backplane without
disturbing system power.

0.05% maximum (Pt

7B34

filter preconditions the RTD signal prior to amplification,
provided by a low drift input amplifier. Amplitude modulation
is used to implement transformer isolation (1500 V rms input­to-output and power). Isolated front-end circuitry power is
supplied by a DC/DC converter. The output section contains a
two-pole low pass filter (-3 dB @ 3 Hz), a buffer amplifier and a
power oscillator. The two-pole output filter and subsequent
buffer ensures that a low noise, low impedance (<1Ω) signal is
available at the output to drive loads to 2 kΩ minimum.

The three input pins of Model 7B34 are fully protected up to
120 V rms line voltage. A 250 uA excitation current is provided
to create an input voltage to the 7B34. This current also
provides the upscale open circuit indication. A one-pole 3 Hz

Figure 2

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7B34 Models Available

Model RTD Sensor(2- or 3-wire) Input Range Output

7B34-01-1
7B34-01-2
7B34-02-1
7B34-02-2
7B34-03-1
7B34-03-2
7B34-04-1
7B34-04-2
7B34-05-1
7B34-05-2
7B34-N-01-1
7B34-N-01-2
7B34-N-02-1
7B34-N-02-2
7B34-C50-01-1
7B34-C50-02-1
7B34-C50-06-1

100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
100 Ω Pt, α = 0.00385
120 Ω Ni, α = 0.00672
120 Ω Ni, α = 0.00672
120 Ω Ni, α = 0.00672
120 Ω Ni, α = 0.00672
50 Ω Cu, α = 0.00214
50 Ω Cu, α = 0.00214
50 Ω Cu, α = 0.00214

Range

-100°C to +100°C +1 V to +5 V ±0.05% span ±0.15% span

-100°C to +100°C 0 V to +10 V ±0.05% span ±0.15% span
0°C to +100°C +1 V to +5 V ±0.05% span ±0.2% span
0°C to +100°C 0 V to +10 V ±0.05% span ±0.2% span
0°C to +200°C +1 V to +5 V ±0.05% span ±0.15% span
0°C to +200°C 0 V to +10 V ±0.05% span ±0.15% span
0°C to +600°C +1 V to +5 V ±0.05% span ±0.1% span
0°C to +600°C 0 V to +10 V ±0.05% span ±0.1% span

-50°C to +350°C +1 V to +5 V ±0.05% span ±0.1% span

-50°C to +350°C 0 V to +10 V ±0.05% span ±0.1% span
0°C to +300°C +1 V to +5 V ±0.12% span ±0.3% span
0°C to +300°C 0 V to +10 V ±0.12% span ±0.3% span
0°C to +200°C +1 V to +5 V ±0.14% span ±0.3% span
0°C to +200°C 0 V to +10 V ±0.14% span ±0.3% span

-100°C to +100°C +1 V to +5 V ±0.10% span ±0.15% span
0°C to +100°C +1 V to +5 V ±0.02% span ±0.15% span

-50°C to +200°C +1 V to +5 V ±0.08% span ±0.15% span

Nonlinearity(maximum) Accuracy

(maximum)

7B34

7B34 Specifications
(typical @ +23°C ±5 °C and Vs = +24 V dc)

Description Model 7B34

Input Range1

RTD T y pes

Standard Temperature Ranges Refer to Model Table
Custom Ranges Not Available*
Output Range Options (RL > 2 kΩ)

Initial @ +25°C Refer to Model Table
Nonlinearity

2

Refer to Model Table

100 Ω Platinum, 2-, 3-wire α = 0.00385
120 Ω Nickel, 2-, 3-wire, α = 0.00672

+1 V to +5 V or 0 V to +10 V

1

Accuracy

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