ANALOG DEVICES 5B38 Service Manual

Isolated, Wide-Bandwidth Strain Gage Input

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FEATURES

Wide-bandwidth Single-Channel Signal Conditioning
Interfaces, Amplifies, and Filters signals from full-bridge and

half-bridge strain-gage transduces between 300Ω and 10kΩ.
Isolated Precision Output of -5V to +5V.
10 kHz bandwidth of the 5B38 ideally suits to measure

signals that vary rapidly with time.
Module circuitry can withstand 240v rms at the input screw-

terminals.
All 5B38 series modules are mix-and-match and Hot

Swappable.

APPLICATIONS

Industrial signal conditioning
Industrial signal isolation
Industrial signal filtering

PRODUCT OVERVIEW

The 5B Series represents an innovative generation of low cost,
high performance plug-in signal conditioners. Designed for
industrial applications, these modules incorporate highly
reliable transformer-based isolation and automated surface­mount manufacturing technology. They are compact,
economical components whose performance exceeds that
available from more expensive devices. Combining 1500 V rms
continuous isolation, +0.05% calibrated accuracy, small size and
low cost, the 5B Series is an attractive alternative to expensive
signal conditioners and in-house designs

All modules are potted and identical in pin-out and size (2.27” x

2.32” x 0.595”). They can be mixed and matched, permitting
users to address their exact needs, and may be “hot swapped
without disturbing field wiring or power. The isolated input
modules provide 0 to +5V or +5V outputs and accept J, K, T, E,
R, S, N, or B type thermocouples.

5B38

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 5B38 Functional Block Diagram

There are also a number of backplanes and mounting sockets
which provide a complete signal conditioning solution for end
users. Each backplane incorporates screw terminals for field
wiring inputs and outputs and cold junction sensors for
thermocouple applications.

These signal conditioners are designed to provide an easy and
convenient solution to signal conditioning problems of both
designers and end users in measurement and control
applications. Typical uses include microcomputer-based
measurement systems, standard data acquisition systems,
programmable controllers, analog recorders and dedicated
control systems. The 5 B series modules are ideally suited to
applications where monitoring and control of temperature,
pressure, f low, rotation and other analog signals are required.

The 5B Series modules and backplanes are approved by Factory
Mutual (FM) and the 5B Series modules are approved by the
Canadian Standards Association (CSA) for use in Class 1,
Division 2, Groups A, B, C, and D locations. These approvals
certify that the 5B Series is suitable for use in locations where a
hazardous concentration of flammable gas may exist only under
fault conditions of operation. Equipment of this category is
called “non-incendive” and they need no special enclosures or
other physical safeguards.

These modules feature complete signal conditioning functions
including 240 V rms input protection, filtering, chopper
stabilized low drift +1 uV/oC amplification, 1500 V rms
isolation, and sensor excitation when required.

All modules feature excellent common mode rejection and
meet industrial transient surge withstand specifications.

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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.

The 5B series modules and backplanes have been tested and
passed the stringent heavy industrial requirements of the
European Union’s electromagnetic compatibility (ENC)
directive – EN50082-1 and EN50081-2. When used according
to installation directions (refer to 5B series User Manual), any
errors caused by EMI/RFI interference will be less than 0.1% of
the full scale 5B measurement range for field strengths up to 10
V/M and frequencies up to 1 GHz.

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 5B38 is a wide-bandwidth single-channel signal
conditioning module that interfaces, amplifies, and filters
signals from full-bridge and half-bridge strain-gage transducers
between 300Ω and 10kΩ. The module provides an isolated
bridge excitation of +10V and a protected, isolated precision
output of -5V to +5V. The 10 kHz bandwidth of the module
ideally suits to measure signals that vary rapidly with time, such
as strain on an automobile chassis during a crash test.

The 5B38 protects the computer side from damage due to field­side over-voltage faults. The module withstands 240V rms at its
input terminals without damage, thereby shielding computer­side circuitry from field-side over-voltage conditions. In
addition, the 5B38 is mix-and-match and hot-swappable with
all 5B Series modules, so can be inserted or removed from any
socket in the same backplane without disrupting system power.

The 5B38-04 contains bridge completion circuitry, so can
function with half-bridge strain gages. For quarter-bridge
requirements, the user must complete the bridge input to the
half-bridge level externally. The factory can configure the
module for a wide range of input ranges (sensitivities).

5B38

bandwidth and yields optimal noise performance for accurate
measurement of small signals in high electrical noise. A
chopper-stabilized input amplifier provides low drift and stable
gain.

Signal isolation by transformer coupling uses a proprietary
modulation technique for linear, stable and reliable
performance. The differential input circuit on the field side is
fully floating, eliminating the need for any input grounding. 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 signal. An
additional benefit, the output section acts as a third floating
port, eliminating possible problems from ground loops and
power-supply noise. The output common must be kept within
+

3V of power common.

A series output switch eliminates the need for external
multiplexing in many applications. The switch is turned on by
an active-low enable input. If the switch is to be on at all times,
the enable-input should be grounded to power common as it is
on the 5B01 and 5B08 backplanes..

A signle-pole anti-aliasing filter resides at each modules input.
A three-pole, low-pass filter in the output stage sets the

.

.

Figure 2

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5B38

5B38 Models Available

Model Input Bridge Type Bridge Range Excitation Sensitivity Output Range

5B38-02

5B38-04

5B38-05

5B38-Custom

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

Full Bridge

Half Bridge

Full Bridge

*

300 Ωto 10 kΩ

300 Ωto 10 kΩ

300 Ωto 10 kΩ

300 Ωto 10 kΩ

+10.0 V 3 mV/V -5 V to +5 V

+10.0 V 3 mV/V -5 V to +5 V

+10.0 V 2 mV/V -5 V to +5 V

+10.0 V * -5 V to +5 V

5B38 Specifications

Description Model 5B38 Full Bridge Model 5B38 Half Bridge

Input Ranges

Standard Ranges ±20 mV (2 mV/V Sensitivity)

Custom Ranges ±10 mV to ±500 mV *

Output Ranges (RL > 50 kΩ)

Initial @ +25°C ±0.08% Span ±10 µV RTI ±0.08% Span ±1 mV RTI

Nonlinearity ±0.02% Span *

Input Offset vs. Temperature ±1 µV/°C *

Output Offset vs. Temperature ±40 µV/°C *

Gain vs. Temperature ±25 ppm of Reading/°C *

Excitation Voltage Output @ full load +10 V ±3 mV *

Load Range

Load Regulation ±5 ppm/mA *

vs. Temperature ±15 ppm/°C *

Half Bridge Voltage Level N/A +5 V ±1 mV

Half Bridge Voltage vs. Temperature N/A ±15 ppm/°C

Input Bias Current ±3 nA *

Power On

Power Off

Overload

Input, 0.1 Hz to 10 Hz Bandwidth 0.4 µV rms 2 µV rms

Input, 10 kHz Bandwidth

Output, 100 kHz Bandwidth 10 mV peak-peak *

±30 mV (3 mV/V Sensitivity)

-5 V to +5 V *

Accuracy2

10 kΩ, minimum; 300 Ω, maximum

Input Resistance

20 MΩ, minimum

40 kΩ, minimum

40 kΩ, minimum

Noise

±70 nV/ Hz ±250 nV/ Hz

±30 mV (3 mV/V Sensitivity)

*

*

*

*

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