7B34-04-2 - Analog Devices

Isolated, Linearized RTD Input

7B34

Rev. 0

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FEATURES

Amplifies, Protects, Filters, and interfaces input voltages

from a wide variety of two and three-wire platinum, copper

and nickel Resistor Temperature Detectors (RTDs).

Module provides a precision output of either +1 V to +5 V or

0 V to +10 V, linear with temperature.

All 7B34 series modules are mix-and-match and Hot

Swappable.

APPLICATIONS

Industrial signal conditioning

Industrial signal amplification

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 -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 pin-

out 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.

FUNCTIONAL BLOCK DIAGRAM

Figure 1. 7B34 Functional Block Diagram

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 rack-

compatible 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.

7B34

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GENERAL DESCRIPTION

The 7B34 is a single-channel signal conditioning module that

interfaces, amplifies and filters input voltages from a wide

variety of two- and three-wire platinum, copper and nickel

Resistor Temperature Detectors (RTDs) and provides a

protected precision output of either +1 V to +5 V or 0 V to +10

V, linear with RTD temperature. Three-wire lead resistance

compensation is provided and 2- or 3-wire RTDs may be used.

RTD excitation current, and a predictable upscale open circuit

indication provide a complete signal conditioning solution.

Model 7B34 features a nonlinearity of +0.05% maximum (Pt

RTDs). 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 160 dB @

50/60 Hz and a normal model rejection (NMR) of 60 dB @

50/60 Hz are provided. Rated to operate with a nominal +24

VDC supply, Model 7B34 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.

The three input pins of Model 7B34 are fully protected up to

120 V rms line voltage. A 250 uA excitation current is provided

to create an input voltage to the 7B34. This current also

provides the upscale open circuit indication. A one-pole 3 Hz

filter preconditions the RTD signal prior to amplification,

provided by a low drift input amplifier. Amplitude modulation

is used to implement transformer isolation (1500 V rms input-

to-output and power). Isolated front-end circuitry power is

supplied by a DC/DC converter. The output section contains a

two-pole low pass filter (-3 dB @ 3 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.

Figure 2

7B34

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7B34 Models Available

Model RTD Sensor(2- or 3-wire) Input Range Output

Range

Nonlinearity(maximum) Accuracy

(maximum)

7B34-01-1 100 Ω Pt, α = 0.00385 -100°C to +100°C +1 V to +5 V ±0.05% span ±0.15% span

7B34-01-2 100 Ω Pt, α = 0.00385 -100°C to +100°C 0 V to +10 V ±0.05% span ±0.15% span

7B34-02-1 100 Ω Pt, α = 0.00385 0°C to +100°C +1 V to +5 V ±0.05% span ±0.2% span

7B34-02-2 100 Ω Pt, α = 0.00385 0°C to +100°C 0 V to +10 V ±0.05% span ±0.2% span

7B34-03-1 100 Ω Pt, α = 0.00385 0°C to +200°C +1 V to +5 V ±0.05% span ±0.15% span

7B34-03-2 100 Ω Pt, α = 0.00385 0°C to +200°C 0 V to +10 V ±0.05% span ±0.15% span

7B34-04-1 100 Ω Pt, α = 0.00385 0°C to +600°C +1 V to +5 V ±0.05% span ±0.1% span

7B34-04-2 100 Ω Pt, α = 0.00385 0°C to +600°C 0 V to +10 V ±0.05% span ±0.1% span

7B34-05-1 100 Ω Pt, α = 0.00385 -50°C to +350°C +1 V to +5 V ±0.05% span ±0.1% span

7B34-05-2 100 Ω Pt, α = 0.00385 -50°C to +350°C 0 V to +10 V ±0.05% span ±0.1% span

7B34-N-01-1 120 Ω Ni, α = 0.00672 0°C to +300°C +1 V to +5 V ±0.12% span ±0.3% span

7B34-N-01-2 120 Ω Ni, α = 0.00672 0°C to +300°C 0 V to +10 V ±0.12% span ±0.3% span

7B34-N-02-1 120 Ω Ni, α = 0.00672 0°C to +200°C +1 V to +5 V ±0.14% span ±0.3% span

7B34-N-02-2 120 Ω Ni, α = 0.00672 0°C to +200°C 0 V to +10 V ±0.14% span ±0.3% span

7B34-C50-01-1 50 Ω Cu, α = 0.00214 -100°C to +100°C +1 V to +5 V ±0.10% span ±0.15% span

7B34-C50-02-1 50 Ω Cu, α = 0.00214 0°C to +100°C +1 V to +5 V ±0.02% span ±0.15% span

7B34-C50-06-1 50 Ω Cu, α = 0.00214 -50°C to +200°C +1 V to +5 V ±0.08% span ±0.15% span

7B34 Specifications

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

Description Model 7B34

Input Range1

RTD Types 100 Ω Platinum, 2-, 3-wire α = 0.00385

120 Ω Nickel, 2-, 3-wire, α = 0.00672

Standard Temperature Ranges Refer to Model Table

Custom Ranges Not Available*

Output Range Options (RL > 2 kΩ) +1 V to +5 V or 0 V to +10 V

Accuracy1

Initial @ +25°C Refer to Model Table

Nonlinearity2 Refer to Model Table

7B34

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Input Offset vs. Temperature ±1 µV/°C

Zero Suppression vs. Temperature ±0.002% (Rz/Rspan)3/°C

Span vs. Temperature ±60 ppm/°C

Output Offset vs. Temperature ±0.002% Span/°C

Lead Resistance Effect ±0.02°C /Ω

Output Noise

5 MHz Bandwidth 10 mV peak

10 Hz to 100 kHz Bandwidth 0.4 mV rms

0.1 Hz to 10 Hz Bandwidth 0.6 µV peak

Bandwidth, -3 dB 3 Hz

Output Rise Time, 10% to 90% Span 250 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 160 dB

Normal Mode Rejection @ 50/60 Hz 60 dB

Input Protection 120 V rms, continuous±35 V dc, continuous

Input Transient Protection ANSI/IEEE C376.90.1-1989

IEEE-STD 472

IEC 255-4, Class II

Output Resistance < 1 Ω

Voltage Output Protection Continuous Short to Ground

Power Supply

Voltage Range, Operating +14 V dc to +35 V dc

Current +25 mA, maximum

Sensitivity ±0.0001%/% of Vs

Mechanical Dimensions 1.663" x 2.11" x 0.563"(42.24 mm x 53.6 mm x 14.3 mm)

Weight 60 grams

Environmental

Temperature Range

Operating -40°C to +85°C

Storage -40°C to +85°C

Relative Humidity, 24 hours 0 to 90% @ +60°C noncondensing

ESD Sensitivity IEC 801-2, Level 2

RFI Susceptibility ±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

Warm-up time required to meet specifications is approximately 10 minutes.

* Contact factory for OEM requirements.

1Includes the combined effects of repeatability, hysteresis, and nonlinearity.

2Nonlinearity is calculated using best-fit straight line method.

3Rz is the value of the RTD resistance at the lowest measurement point. Rspan is the change in resistance over the measurement span.

Specifications subject to change without notice.

7B34

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PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS

Figure 3 7B34 Input Field Connections

Table 1. Pin Function Descriptions—

No.

Input Module Function Output Module Function

0 SENSOR INPUT NOT USED

1 INPUT HIGH OUTPUT HIGH

2 INPUT LOW OUTPUT LOW

3 POWER SUPPLY (DC) POWER SUPPLY (DC)

4 OUTPUT VOLTAGE INPUT VOLTAGE

5 OUTPUT & POWER

COMMON

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.

7B34

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OUTLINE DIMENSIONS

Figure 5. Outline Dimensions

7B34

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NOTES

7B34

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NOTES

registered trademarks are the property of their respective companies.

D05176-0-10/04(0)