5B37 Isolated Thermocouple Input


5b37-j-01The 5B37 is a single-channel signal conditioning module that interfaces, amplifies and filters J, K, T, E, R, S, B, N, and C-type thermocouple and provides an isolated and protected precision output of 0 to +5 V.

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 ±0.25°C @ +25°C ambient temperature. The module generates a predictable upscale signal to indicate an open thermocouple; for a downscale response, connect a 47 MΩ, 0.25 W resistor across screw terminals 1 and 3.

The 5B37 protects the computer side from damage due to field-side overvoltage faults. All models withstand 240 V rms at their input terminals without damage, thereby shielding computer-side circuitry from field-side overvoltage conditions. Further, the 5B37 is mix-and-match and hot-swappable with other 5B Series modules, so can be inserted or removed from any socket in the same backplane without disrupting system power.

Inside the 5B37 Module 

A chopper-stabilized input amplifier provides low drift and stable gain. At the amplifier input, a stable, laser-trimmed zero-scale input voltage is subtracted from the input signal to set the zero-scale value. For user convenience, the zero can be optionally factory-set to meet custom needs. This allows suppression of a zero-scale input value many times larger than the total span for precise expanded-scale measurements.

Internal multi-pole lowpass filtering with a four-Hz cutoff (-3 dB) provides 60 dB of normal-mode rejection (noise on signal) and enhancement of common-mode rejection (noise on signal return) at 60 Hz, enabling accurate measurement of small signals in high electrical noise.

Signal isolation by transformer coupling uses a proprietary modulation technique for linear, stable and reliable performance. The differential input circuit on the field side is fully floating, eliminating the need for any input grounding. 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 signal. The output common must be kept within 3 V of power common.

Convenience Features 

A series output switch eliminates the need for external multiplexing in many applications. The switch is turned on by an active-low enable input. The enable input should be grounded to power common if the output need not be switched, as on the 5B01 and 5B08 backplanes.

Input and Output Ranges

5B37 Functional Block Diagram

Figure 1. 5B37 Functional Block Diagram

5B37 Input Field Connections

Figure 2. 5B37 Input Field Connections

Input Types
Output Range
Thermocouple Types: 
J, K, T, E, R, S, B, N, C
0 to +5 V 
(-5 V to +5 V - custom)

5B37 Models Available

Model  Input Type  Input
Order Now 5B37-J-01
Type J
-100°C to +760°C (-148°F to +1400°F)
0 V to +5 V
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Type K -100°C to +1350°C (-148°F to +2462°F)
0 V to +5 V
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Type T -100°C to +400°C (-148°F to +752°F)
0 V to +5 V
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5B37-E-04 Type E 0°C to +900°C (+32°F to +1652°F)
0 V to +5 V
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5B37-R-05 Type R 0°C to +1750°C (+32°F to +3182°F) 0 V to +5 V
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Type S
0°C to +1750°C (+32°F to +3182°F)
0 V to +5 V
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Type B
0°C to +1800°C (+32°F to +3272°F)
0 V to +5 V
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Type N
0°C to +1300°C (+32°F to +2372°F)
0 V to +5 V

Type J, K, T, E, R, S, B, N, C    *

* Custom Input/Output ranges are available. Refer to the Configuration Guide.

5B37 Specifications

5B37 Specifications 
(typical @ +25°C and Vs = +5 V dc)

Description  Model 5B37
Input Ranges
Standard Ranges
Refer to Model Table
Custom Ranges
±5 mV to ±500 mV
Output Range (RL > 50 kΩ)4
-5 V to +5 V or 0 to +5 V
Initial @ +25°C
±0.05% Span ±10 µV RTI ±0.05% of Vz1 +CJC Sensor Error
±0.02% Span
Input Offset vs. Temperature ±1 µV/°C
Output Offset vs. Temperature
±20 µV/°C
Gain vs. Temperature
±0.0025% of Reading/°C
 Cold Junction Compensation
Initial Accuracy @ +25°C3
±0.25°C (±0.75°C, maximum)
Accuracy, +5°C to +45°C
±0.5°C (±0.0125°C/°C)
Input Bias Current
 -25 nA
Input Resistance
Power On 5 MΩ
Power Off 40 kΩ
Overload 40 kΩ
Input, 0.1 Hz to 10 Hz Bandwidth
0.2 µV rms
Output, 100 kHz Bandwidth
200 µV rms
Bandwidth, -3 dB
4 Hz
Output Rise Time, 10% to 90% Span
200 ms
Common-Mode Voltage (CMV)
Input-to-Output, Continuous
1500 V rms, maximum
Output-to-Power, Continuous
±3 V, maximum
Transient ANSI/IEEE C37.90.1-1989
Common-Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz
160 dB
Normal Mode Rejection (NMR), 50/60 Hz
60 dB
Input Protection
240 V rms, maximum
ANSI/IEEE C37.90.1-1989
Output Resistance
50 Ω
Voltage Output Protection
Continuous Short to Ground
Output Selection Time
6 µs @ Cload = 0 to 2,000 pF
Output Enable Control
Max Logic "0"  +1 V
Min Logic "1"
+2.5 V
Max Logic "1"
+36 V
Input Current "0"
0.4 mA
Open Input Response
Open Input Response Time 10 seconds
Power Supply Voltage
+5 V ±5%
Power Supply Current
30 mA
Power Supply Sensitivity, RTI
±2 µV/% of Vs
Mechanical Dimensions
2.275" x 2.375" x 0.595"
(57.8 mm x 59.1 mm x 15.1 mm)
Temperature Range
   Rated Performance -25°C to +85°C
   Operating -40°C to +85°C
   Storage -40°C to +85°C
Relative Humidity
0 to 93% @ +40°C noncondensing
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

1 Vz is the nominal input voltage that results in a 0 V output.
2 Includes the combined effects of repeatability, hysteresis, and nonlinearity and assumes RL > 50 kΩ. Loads heavier than 50 kΩ will degrade nonlinearity and gain temperature coefficient.
3 When used with the model AC1361 CJC sensor (see Accessories section), which is provided on each channel of 5B Series backplanes and mounting cards.
4 The output common must be kept within ±3 V of power common.

Specifications subject to change without notice.