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Isolated Process Current Input with Loop Power 7B35
FEATURES
Single-channel signal conditioning current input module that interfaces with two-wire transmitters. Module provides a precision output of either +1 V to +5 V or +2 V to +10 V, linear with temperature. Features a isolated 24 VDC loop supply for driving the transmitter. All 7B35 series modules are mix-and-match and Hot Swappable.
FUNCTIONAL BLOCK DIAGRAM
APPLICATIONS
Industrial signal isolation Industrial signal filtering
Figure 1. 7B35 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 -40oC to +85oC 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.
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 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.
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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. www.analog.com Tel: 781.329.4700 Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved.
7B35 GENERAL DESCRIPTION
The 7B35 is a single-channel signal conditioning current input module that interfaces with two-wire transmitters, providing an isolated protected precision output of either +1 V to +5 V or +2 V to +10 V. Model 7B35 features an isolated 24 VDC loop power supply for driving the transmitter. 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 105 dB @ 50/60 Hz is provided. Rated to operate with a nominal +24 VDC supply, Model 7B35 is mixand-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 two input pins of Model 7B35 are each fully protected up to 120 V rms. The current input signal is converted to a voltage, then filtered by a one-pole 100 Hz filter. 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 isolated transmitter loop power supply is unregulated and will provide a voltage that is proportional to the voltage used to power the 7B35 module. The isolated voltage provided by the 7B35 is between 13 VDC and 34 VDC for loop currents between 4 mA and 20 mA and supply voltages between 20.4 VDC and 26.4 VDC. The output section contains a two-pole low-pass filter (-3 dB @ 100 Hz), a buffer amplifier and power oscillator. The two-pole output filter and subsequent buffer ensures that a low noise, low impedance (<1) signal is available at the output to drive loads down to 2k.
Figure 2
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7B35
7B35 Models Available
Model 7B35-01-1 7B35-01-2 Input Range +4 mA to +20 mA1 +4 mA to +20 mA
1
Output Range +1 V to +5 V +2 V to +10 V
7B35 Specifications (typical @ +23C 5C and Vs = +24 V dc)
Description Input Range1 Standard Range Custom Ranges Standard Range Custom Ranges Input Loop Supply Voltage, Isolated Output Range (RL > 2 k) 4 mA to 20 mA Not Available* 4 mA to 20 mA Not Available* +24 V dc @ ILoop = 20 mA +1 V to +5 V or +2 V to +10 V Accuracy1 Initial @ +25C Nonlinearity
2
Model 7B35
0.01% Span (0.1% Span, maximum) 0.02% Span, maximum N/A3 40 ppm/C 0.003% span/C Output Noise
Input Offset vs. Temperature Span vs. Temperature Output Offset vs. Temperature
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
6 mV peak 0.9 mV rms 4 V peak 100 Hz 5 ms Common-Mode Voltage (CMV)
Input-to-Output and Power
1500 V rms continuous Common Mode Rejection (CMR)
Input-to-Output and Power @ 50/60 Hz Input Protection Input Transient Protection
105 dB 120 V rms, continuous 35 V dc, continuous ANSI/IEEE C376.90.1-1989 IEEE-STD 472 IEC 255-4, Class II
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7B35
Output Resistance Voltage Output Protection <1 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
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 Input offset term is included in the output offset specification. Specifications subject to change without notice.
-40C to +85C -40C to +85C 0 to 90% @ +60C non-condensing IEC 801-2, Level 2 0.5% Span error @ 400 MHz, 5 Watt, 3 ft
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7B35 PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS
Figure 3 7B35 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.
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7B35 OUTLINE DIMENSIONS
Figure 5. Outline Dimensions
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7B35 NOTES
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7B35 NOTES
(c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective companies. D05177-0-10/04(0)
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