3B47 Isolated, Linearized, Thermocouple Input


Model 3B47-J-03The 3B47 is a single-channel isolated thermocouple signal-conditioning module which interfaces, amplifies, isolates, protects, linearizes and filters analog input voltages from a J, K, T, E, R, S or B-type thermocouple. The thermocouple input signal is internally linearized to provide an output voltage which is linear with 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 peak of galvanic transformer-based isolation with a common mode rejection (CMR) of 160 dB @ 50/60 Hz and a normal mode rejection (NMR) of 60 dB @ 50/60 Hz are provided. This plug-in, mix-and-match, hot-swappable module is easily field calibrated via front-panel zero and span adjustments.

Inside the 3B47 Module

A chopper-stabilized low-drift input amplifier assures stable long-term stability. At the amplifier input, a zero-scale input voltage is subtracted from the input signal to set the zero-scale value. For user convenience, the zero and span optionally can be factory configured to meet custom needs (Model 3B37-CUSTOM). Zero suppression can exceed 100% of the input range. This enables suppression of a zero-scale input value many times larger than the total span for precise expanded-scale measurements of a selection portion of an input signal. The differential input circuit on the field side is fully floating, eliminating the need for any input grounding. Signal isolation by transformer coupling uses a proprietary modulation technique for linear, stable and reliable performance A demodulator on the computer side of the signal transformer recovers the original signal, which is then filtered and buffered to provide a low-noise, low-impedance output voltage.

Accurate and System-Ready

Internal cold-junction compensation largely corrects errors arising from parasitic thermocouples formed by thermocouple connection to the input screw terminals, providing an accuracy of ±0.5°C over the +5°C to + 45°C ambient temperature range. The module generates a predictable upscale signal to indicate an open thermocouple; for a downscale response, connect a 47 MΩ, 0.25 Watt resistor across screw terminals 2 and 4 on the 3B Series backplane.

Input and Output Ranges

3B47 Functional Block Diagram

Figure 1. 3B47 Functional Block Diagram

3B47 Input Field Connections

Figure 2. 3B47 Input Field Connections

Input Type
Output Range
Thermocouple Types: J, K, T, E, R, S, B
0 to +10 V

3B47 Models Available

Model  Input Type  Input Range Output Range Accuracy1
Order Now 3B47-J-01
Type J 0°C to +760°C (32°F to +1400°F)
0 V to +10 V
Order Now
Type J -100°C to +300°C (-148°F to +572°F)
0 V to +10 V
Order Now
Type J 0°C to +500°C (+32°F to +932°F)
0 V to +10 V 0.36°C
Order Now
Typel K 0°C to +1000°C (+32°F to +1832°F) 0 V to +10 V 1.0°C
Order Now
Type K 0°C to +500°C (+32°F to +932°F)
0 V to +10 V
Order Now
Type T -100°C to +400°C (-148°F to +752°F)
0 V to +10 V
Order Now
Type T 0°C to +200°C (+32°F to +392°F)
0 V to +10 V 0.3°C
Order Now
Type E 0°C to +1000°C (+32°F to +1832°F)
0 V to +10 V
Order Now
Type R +500°C to +1750°C (+932°F to +3182°F)
0 V to +10 V
Order Now
Type S +500°C to +1750°C (+932°F to +3182°F) 0 V to +10 V 1.5°C
Order Now
Type B +500°C to +1800°C (+932°F to +3272°F) 0 V to +10 V 3.3°C

Type J, K, T, E, R, S, or B  * * *

The CJC sensor accuracy (refer to specification table) should be added to the module accuracy when computing system accuracy.
* Custom Input/Output ranges are available. Refer to configuration guide.

3B47 Specifications

(typical @ +25°C and ±15 V dc, and +24 V dc Power)

Description  Model 3B37
Input Range
Thermocouple Types J, K, T, E, R, S, B
Standard Ranges
Refer to Model Table
Custom Ranges
±5 mV to ±500 mV
Output Range1
Voltage (RL > 2K)
0 V to +10 V
Initial @ +25°C
See Model Table
Stability vs. Temperature
Voltage Output
   Zero ±0.02°C/°C
   Span ±25 ppm of Reading/°C
Zero and Span Adjustment Range3
±5% of Span
Cold Junction Compensation (CJC)4
Initial Accuracy @ +25°C
±0.5 °C
Accuracy vs. Temperature, +5°C to +45°C
±0.5°C (±0.0125°C/°C)
Input Bias Current +15 nA
Input Resistance
15 MΩ
Input, 0.1 Hz to 10 Hz Bandwidth
0.2 µV rms
Output, 100 kHz Bandwidth
100 µV rms
Bandwidth, -3 dB
3 Hz
Output Rise Time, 10% to 90% Span 200 ms
Open Input Response
Open Input Detection Time 10 seconds
Common-Mode Voltage (CMV)  
Input-to-Output, Continuous
±1500 V peak, maximum
ANSI/IEEE C37.90.1-1989
 Common Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz 160 dB
Normal Mode Rejection, 50/60 Hz 60 dB
Input Protection  
220 V rms maximum
 Transient ANSI/IEEE C37.90.1-1989
Voltage Output Protection Continuous Short to Ground
Current Output Protection
130 V rms, continuous
Power Supply Voltages
Rated Operation ±(11.5 V dc to 16.5 V dc)
Current +16 mA, -14 mA
Sensitivity ±0.01% span/V
Mechanical Dimensions
3.15" x 3.395" x 0.775"
(80.0 mm x 86.2 mm x 19.7 mm)
Temperature Range
   Rated Performance -25°C to +85°C
   Storage -55°C to +85°C
Relative Humidity
0 to 95% @ +60°C noncondensing
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

Current output is not available with model 3B47.
2 Includes the combined effects of repeatability, hysteresis, and nonlinearity.
3 A wide range of zero suppression and span adjustment is available to enable field calibration.
4 When used with the CJC temperature sensor provided on the 3B Series backplane.
Specifications subject to change without notice.