Analog Devices 5B Series Signal Conditioning Overview

Introduction

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 surface-mount 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 pinout 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 +5 V or ±5 V outputs and accept J, K, T, E, R, S, N or B type thermocouples; 100 ohm platinum, 10 ohm copper and 120 ohm nickel RTDs, frequency inputs, potentiometer, slide wire, full or half bridge strain gage, 2-wire transmitter, mV, volt, 4-20 mA or 0-20 mA, and wide bandwidth (10 kHz) mV and volt signals. These modules feature complete signal conditioning functions including 240 V rms input protection, filtering, chopper stabilized low drift ±1 µV/°C amplification, 1500 V rms isolation, linearization for RTD and thermocouple (with model 5B47) inputs and sensor excitation when required. The output module converts a 0 to + 5 V or -5 V to +5 V input to an isolated 4-20 mA or 0-20 mA process current signal. All modules feature excellent common mode rejection and meet industrial transient surge withstand specifications.

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. Nineteen-inch rack compatible units that can hold up to sixteen modules are available.

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 5B Series modules are ideally suited to applications where monitoring and control of temperature, pressure, flow, rotation and other analog signals are required.

FM, CSA and CE Approvals

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 I, 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 "nonincendive" and they need no special enclosures or other physical safeguards.

The 5B Series modules and backplanes have been tested and passed the stringent heavy industrial requirements of the European Union's electromagnetic compatibility (EMC) 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 (typical @ +25°C), for field strengths up to 10 V/M and frequencies up to 1 GHz.

Design Features and User Benefits

System Design
It is easy for system designers to apply the functionally complete 5B Series modules in their own circuit board or backplane. These modules feature a simple pinout, plug into widely available sockets and are secured with self-contained mounting screws. Other features, which can be used to minimize system interface cost, have also been incorporated in the 5B Series design. Each input module has an output switch which is controlled by a TTL-compatible enable input, eliminating the need for an external multiplexer. Each output module has a track and hold input which permits a single DAC to serve numerous current output channels. For thermocouple applications, cold junction compensation sensors are available.

Subsystem Solution
The 5B Series provides a complete signal conditioning solution. A family of backplanes, pre-calibrated plug-in modules, direct sensor interface via screw terminal connections, high level outputs, and ribbon cable system interface result in easy integration into any system. For thermocouple applications, high accuracy cold junction compensation sensing is provided on each backplane channel. A general subsystem application is outlined in Figure 1.

Flexibility
The 5B Series can be easily tailored to meet each user's needs. These plug-in signal conditioners can be mixed and matched to provide I/O for various process sensors and actuators. Many standard configurations of each module are available, and for added flexibility, factory laser trimmed custom units can be supplied. A wide zero suppression capability allows a user to map any portion of the input signal into the full output span permitting improved system resolution within a selected measurement range.

High Reliability
The 5B Series was designed to assure maximum reliability under real-world conditions. The modules are specified over the -25°C to +85°C temperature range. Each module is potted; there are no adjustment potentiometers which could introduce mechanical and human errors that impair system integrity. All field wiring termination, including sensor inputs, excitation and current outputs, are protected against continuous 240 V rms line voltage. This prevents a fault from damaging the module, the backplane or other devices connected to the system. The modules also provide protection against high common mode voltages and are designed to meet the standards for transient voltage protection. Gold-plated pin and socket connections are used throughout the system to ensure connection reliability.

High Performance
The high quality signal conditioning features include ±0.05% span initial accuracy, nonlinearity of only ±0.02% span, and chopper-based amplification which assures low drift (±1 µV/°C) and excellent long-term stability. Low drift sensor excitation is provided when required, and the model 5B34 RTD and model 5B47 thermocouple modules provide an output which is linear with input sensor temperature.

High Noise Rejection
The 5B Series modules were designed to accurately process low level signals in electrically noisy environments by providing 1500 V rms continuous of transformer-based isolation which eliminates ground loops, protects against transients and solves common-mode voltage problems. To further preserve signal integrity, 160 dB of common-mode rejection, 60 dB of normal mode rejection and excellent RFI/EMI immunity are provided.

Small Size
Each 5B Series module measures only 2.275" x 2.325" x 0.595" resulting in space savings for both system designers and end users: each module occupies 1.35 square inches of board space and a 16-channel backplane occupies only 3.5" in a 19" rack.

Figure 1. Block Diagram of a General Measurement and Control Application Using the 5B Series.

Features

Rugged, Compact, Low Cost Signal Conditioners

Industry Standard Package and Functionality

Complete Signal Conditioning Function

Floating, Differential Input with 240 V rms Field Wiring Protection

Input-to-Output CMV Isolation : 1500 V rms continuous

Filtering : High 50 Hz and 60 Hz Normal Mode Rejection

Amplification

Zero Suppression

RFI/EMI Immunity

High Accuracy: ±0.05%

Low Drift: ±1 µV/°C

-25°C to +85°C Operating Range

Mix and Match Module Capability

Custom Ranged Modules Available

FM and CSA Approved

Approved For Use In Class I, Division 2,
Groups A, B, C and D Locations

CE Approved

Heavy Industrial Standards: EN50081-2
and EN50082-1

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