Isolated, Linearized RTD Input
7B34
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.
FUNCTIONAL BLOCK DIAGRAM
APPLICATIONS
Industrial signal conditioning
Industrial signal amplification
Industrial signal filtering
Figure 1. 7B34 Functional Block Diagram
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 to
+85
o
C industrial temperature range. All 7B Series modules are
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 pin-
out 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.
The modules feature a maximum nonlinearity of +0.02% and
are factory calibrated to guarantee a maximum accuracy
specification of +0.1%.
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 rack-
compatible 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.
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.
www.analog.com
Tel: 781.329.4700
Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
7B34
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 +0.05% maximum (Pt
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.
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
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 input-
to-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.
Figure 2
Rev. 0 | Page 2 of 8
7B34
7B34 Models Available
Model
RTD Sensor(2- or 3-wire)
Input Range
Output
Range
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
0 V to +10 V
+1 V to +5 V
+1 V to +5 V
+1 V to +5 V
Nonlinearity(maximum)
Accuracy
(maximum)
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.05% span
±0.12% span
±0.12% span
±0.14% span
±0.14% span
±0.10% span
±0.02% span
±0.08% span
±0.15% span
±0.15% span
±0.2% span
±0.2% span
±0.15% span
±0.15% span
±0.1% span
±0.1% span
±0.1% span
±0.1% span
±0.3% span
±0.3% span
±0.3% span
±0.3% span
±0.15% span
±0.15% span
±0.15% span
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
-100°C to +100°C
-100°C to +100°C
0°C to +100°C
0°C to +100°C
0°C to +200°C
0°C to +200°C
0°C to +600°C
0°C to +600°C
-50°C to +350°C
-50°C to +350°C
0°C to +300°C
0°C to +300°C
0°C to +200°C
0°C to +200°C
-100°C to +100°C
0°C to +100°C
-50°C to +200°C
7B34 Specifications
(typical @ +23°C ±5 °C and V
s
= +24 V dc)
Description
Input Range1
RTD Types
100
Ω
Platinum, 2-, 3-wire
α
= 0.00385
120
Ω
Nickel, 2-, 3-wire,
α
= 0.00672
Standard Temperature Ranges
Custom Ranges
Output Range Options (R
L
> 2 kΩ)
Refer to Model Table
Not Available*
+1 V to +5 V or 0 V to +10 V
Accuracy
1
Initial @ +25°C
Nonlinearity
2
Refer to Model Table
Refer to Model Table
Rev. 0 | Page 3 of 8
Model 7B34
7B34
Input Offset vs. Temperature
Zero Suppression vs. Temperature
Span vs. Temperature
Output Offset vs. Temperature
Lead Resistance Effect
±1 µV/°C
±0.002% (R
z
/R
span
)3/°C
±60 ppm/°C
±0.002% Span/°C
±0.02°C /Ω
Output Noise
5 MHz Bandwidth
10 Hz to 100 kHz Bandwidth
0.1 Hz to 10 Hz Bandwidth
Bandwidth, -3 dB
Output Rise Time, 10% to 90% Span
10 mV peak
0.4 mV rms
0.6 µV peak
3 Hz
250 ms
Common-Mode Voltage (CMV)
Input-to-Output and Power
Common Mode Rejection (CMR)
Input-to-Output and Power @ 50/60 Hz
Normal Mode Rejection @ 50/60 Hz
Input Protection
Input Transient Protection
160 dB
60 dB
120 V rms, continuous±35 V dc, continuous
ANSI/IEEE C376.90.1-1989
IEEE-STD 472
IEC 255-4, Class II
<1
Ω
Continuous Short to Ground
Power Supply
Voltage Range, Operating
Current
Sensitivity
Mechanical Dimensions
Weight
+14 V dc to +35 V dc
+25 mA, maximum
±0.0001%/% of Vs
1.663" x 2.11" x 0.563"(42.24 mm x 53.6 mm x 14.3 mm)
60 grams
Environmental
Temperature Range
Operating
Storage
Relative Humidity, 24 hours
ESD Sensitivity
RFI Susceptibility
-40°C to +85°C
-40°C to +85°C
0 to 90% @ +60°C noncondensing
IEC 801-2, Level 2
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft
1500 V rms, continuous
Output Resistance
Voltage Output Protection
Warm-up time required to meet specifications is approximately 10 minutes.
* Contact factory for OEM requirements.
1
Includes the combined effects of repeatability, hysteresis, and nonlinearity.
2
Nonlinearity is calculated using best-fit straight line method.
3
Rz is the value of the RTD resistance at the lowest measurement point. R
span
is the change in resistance over the measurement span.
Specifications subject to change without notice.
Rev. 0 | Page 4 of 8
7B34
PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS
Figure 3 7B34 Input Field Connections
Table 1. Pin Function Descriptions—
Pin
No.
0
1
2
3
4
5
Input Module Function
SENSOR INPUT
INPUT HIGH
INPUT LOW
POWER SUPPLY (DC)
OUTPUT VOLTAGE
OUTPUT & POWER
COMMON
Output Module Function
NOT USED
OUTPUT HIGH
OUTPUT LOW
POWER SUPPLY (DC)
INPUT VOLTAGE
INPUT AND POWER
COMMON
Figure 4 . Model 7B Series Module, with pin-out assignments.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human
body and test equipment and can discharge without detection. Although this product features proprietary ESD
protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges.
Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 5 of 8
