Isolated, Linearized Thermocouple Input 7B47
FEATURES
Interfaces, amplifies and filters input voltages from a J, K, T, E, R, S, B or N-type thermocouple. Module provides a precision output of either +1 V to +5 V or 0 V to +10 V, linear with input temperature. All 7B47 series modules are mix-and-match and Hot Swappable.
FUNCTIONAL BLOCK DIAGRAM
APPLICATIONS
Industrial signal conditioning Industrial signal isolation Industrial signal filtering
Figure 1. 7B47 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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7B47 GENERAL DESCRIPTION
The 7B47 is a single-channel signal conditioning module that interfaces, amplifies and filters input voltages from a J, K, T, E, R, S, B, or N-type thermocouple and provides an isolated and protected precision output of either +1V to +5V or 0 to +10 V, linear with input temperature. High accuracy internal cold junction compensation and a predictable upscale open circuit indication provide a complete signal conditioning solution. 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 of 160 dB @ 50/60 Hz and a normal mode rejection (NMR) of 60 dB @ 50/60 Hz are provided. Rated to operate with a nominal +24 VDC supply, Model 7B47 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 7B47 are fully protected up to 120 V rms line voltages. A one-pole 3 Hz filter preconditions the thermocouple signal prior to amplification, provided by a low drift input amplifier. Cold junction compensation (CJC) is implemented using a thermistor temperature sensor embedded under the input screw terminal block on a 7B Series backplane. A voltage reference source acts to offset the thermocouple signal in accordance with the specified lower bound on the input temperature range. A current source provides the upscale open circuit indication. 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 demodulator, linearizer. 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 ( 2 kΩ) J, K, T, E, R, S, B, N Refer to Model Table Not Available* +1 V to +5 V or 0 V to +10 V Accuracy1 Initial @ +25°C Input Offset vs. Temperature Zero Suppression vs. Temperature Span vs. Temperature Output Offset vs. Temperature Refer to Model Table ±0.5 µV/°C ±0.005% (Vz)3/°C ±40 ppm/°C ±0.002% Span/°C Cold Junction Compensation Accuracy , over +5°C to +45°C ambient Input Bias Current
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Model 7B47
±1.0°C, maximum +25 nA Input Resistance
Power ON Power OFF
10 MΩ 30 kΩ, minimum Output Noise
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
7 mV peak 1 mV rms 0.5 µV peak 3 Hz 150 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 Normal Mode Rejection @ 50/60 Hz Input Protection Input Transient Protection
160 dB 60 dB 120 V rms, continuous ±35 V dc, continuous ANSI/IEEE C376.90.1-1989 IEEE-STD 472 IEC 255-4, Class II
