Analog Devices B21 0 (2) Datasheet

Isolated High Level Voltage Input

FEATURES

Unity gain single-channel signal conditioning module that
interfaces, filters, and isolates a +

Features a nonlinearity of +
accuracy of +

All 7B21 series modules are mix-and-match and Hot
Swappable.

0.1% maximum.

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

C industrial temperature range.

+85

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 high­level 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 hot­swapped 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.

10 Volt input signal.

0.02% maximum and an

o

C to

7B21

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 7B21 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%.

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
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Tel: [phone]
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

www.analog.com

GENERAL DESCRIPTION

The 7B21 is a unity gain single-channel signal conditioning
module that interfaces, filters and isolates a +10 Volt input
signal and provides a protected precision output of +10 Volt.
Model 7B21 features a nonlinearity of +0.02% maximum and an
accuracy of +0.1% maximum (+0.01% typical). 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 100 dB @ 50/60 Hz is
provided. Rated to operate with a nominal +24 VDC supply,
Model 7B21 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.

7B21

Isolated front-end circuitry power is supplied by a DC/DC
converter. The output section contains a two-pole low pass filter
(-3 dB @ 300 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.

.

The floating differential input of Model 7B21 is fully protected
up to 120 V rms line voltage. A one-pole 300 Hz filter
preconditions the input signal prior to a low drift differential
input amplifier. Amplitude modulation is used to implement
transformer isolation (1500 V rms input-to-output and power).

Figure 2

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7B21 Models Available

Model Input Range Output Range

7B21

7B21 Specifications

(typical @ +23°C ±5°C and V

Description Model 7B21

Standard Ranges -10 V to +10 V
Custom Ranges Not Available*
Output Range Options (RL > 2 kΩ)

Initial @ +25°C ±0.01% Span (±0.1% Span, maximum)
Nonlinearity
Input Offset vs. Temperature N/A3
Span vs. Temperature ±35 ppm/°C
Output Offset vs. Temperature ±0.001% Span/°C
Input Bias Current 30 pA (200 pA, maximum)

Power ON
Power OFF

5 MHz Bandwidth 6 mV peak
10 Hz to 100 kHz Bandwidth 1.5 mV rms

0.1 Hz to 10 Hz Bandwidth 6 µV peak
Bandwidth, -3 dB 300 Hz
Output Rise Time, 10% to 90% Span 1 ms

Input-to-Output and Power 1500 V rms continuous

Input-to-Output and Power @ 50/60 Hz 100 dB
Input Protection 120 V rms, continuous

Input Transient Protection ANSI/IEEE C376.90.1-1989

Output Resistance
Voltage Output Protection Continuous Short to Ground

2

±0.02% Span, maximum

-10 V to +10 V -10 V to +10 V

= +24 V dc)

s

Input Ranges

-10 V to +10 V

1

Accuracy

Input Resistance

Output Noise

Common-Mode Voltage (CMV)

Common Mode Rejection (CMR)

2 MΩ
30 kΩ, minimum

±35 V dc, continuous

IEEE-STD 472
IEC 255-4, Class II

< 1 Ω

7B21

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