ANALOG DEVICES 7B39 Service Manual

Isolated, Process Current Output

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FEATURES

Interfaces, isolates and filters a 0 V to + 10 V or +1 V to +5 V
input signal.

Provides an isolated process current output of 0 mA to 20
mA or 4 mA to 20 mA across loads of 0 Ω to 850 Ω .

All 7B39 series modules are mix-and-match and Hot
Swappable.

APPLICATIONS

Industrial signal conditioning
Industrial signal isolation
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

+85

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 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

7B39

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 7B39 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%.

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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.

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GENERAL DESCRIPTION

The 7B39 is a single-channel signal conditioning current output
module that interfaces, isolates and filters a 0 V to +10 V or +1
V to +5 V input signal and provides an isolated process current
output of 0 mA to 20 mA or 4 mA to 20 mA across loads of 0 Ω
to 850 Ω . The output current appears at the 7B Series backplane
screw terminal block. Model 7B39 features a nonlinearity of
+

0.02% maximum and an accuracy of +0.1% maximum

(+

0.01% typical). Providing 1500 V rms of galvanic transformer
based isolation, output-to-input and power, the 7B39 offers a
common mode rejection (CMR) of 110 dB @ 50/60 Hz to
preserve the integrity of low level signals in noisy environments.
The 7B39 is mix-and-match and hot-swappable with other 7B
Series modules, so it can be inserted or removed from any
socket in the same backplane without disturbing system power.
Model 7B39 is rated to operate with a nominal +24 VDC supply.

The input signal from the user’s system is buffered and then
used to modulate the amplitude of a square wave carrier. The
modulated signal is transmitted across the signal transformer
and demodulated to retrieve the original input voltage signal.
This voltage is then filtered by a two-pole low pass 100 Hz filter,
buffered and converted to a current output signal. The nominal

7B39

+24 VDC module supply voltage powers the input side of the
7B39. The oscillator on the input side provides the square wave
carrier signal used by the modulator and also drives the power
transformer. The signal at the secondary of the transformer is
used in the demodulator and is also converted to a DC voltage
that powers the circuit on the module’s output. The floating
isolated current output of Model 7B39 is fully protected to 120
V rms line voltage.

Figure 2

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7B39 Models Available

Model Input Range Output Range

7B39-01

7B39-02

7B39 Specifications

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

Description Model 7B39

+1 V to +5 V +4 mA to +20 mA

0 V to +10 V 0 mA to +20 mA

7B39

Output Range (R

Standard Range 0 mA to 20 mA or 4 mA to 20 mA

Custom Ranges Not Available*

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

Initial @ +25°C ±0.01% Span (±0.1% Span, maximum)

Nonlinearity2 ±0.02% Span, maximum

Span vs. Temperature ±25 ppm/°C

Output Offset vs. Temperature ±0.0035% Span/°C

Power ON

Model 7B39-01

Model 7B39-02

Power OFF

5 MHz Bandwidth 160 µA peak

10 Hz to 100 kHz Bandwidth 4 µA peak

10 Hz to 100 kHz Bandwidth 25 nA peak

Bandwidth, -3 dB 100 Hz

Output Rise Time, 10% to 90% Span 3 ms

Output-to-Input and Power 1500 V rms continuous

Output-to-Input and Power @ 50/60 Hz 110 dB

Input Protection ±35 V dc, continuous

Ouput Transient Protection ANSI/IEEE C376.90.1-1989

= 0 Ω to 850 Ω)

L

(30 mA, maximum)

Accuracy1

Input Resistance

2 M Ω

40 k Ω

30 k Ω, minimum

Output Noise

Common-Mode Voltage (CMV)

Common Mode Rejection (CMR)

120 V rms, continuous

IEEE-STD 472
IEC 255-4, Class II

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