5B47

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 5B47 is a single-channel signal conditioning module that

interfaces, amplifies and filters J, K, T, E, R, S, and B-type

thermocouple. The module provides an isolated and protected

precision output of 0 to + 5 V.

The 5B47 internally linearizes its input signal to provide an

output that is linear with temperature. Accuracy for each type of

sensor is specified in the 5B47 model table. (See Model 5B37 for

non-linearized conditioning of thermocouple signals.)

Accurate and System-Ready

- Internal cold-junction

compensation largely corrects errors arising from parasitic

thermocouples formed by thermocouple connection to the

predictable upscale signal to indicate an open thermocouple; for

a downscale response, connect a 20MΩ, 0.25W resistor across

screw terminals 1 and 3.

The 5B47 protects the computer side from damage due to field-

side over-voltage faults. All models withstand 240V rms at their

input terminals without damage, thereby shielding computer-

side circuitry from field-side over-voltage conditions. Further,

the 5B47 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 5B47 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 low-pass filtering with a 4-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.

A series output switch eliminates the need for external

multiplexing in many applications. The switch is turned on by

an active-low enable input. If the switch is to be on at all times,

the enable-input should be grounded to power common as it is

on the 5B01 and 5B08 backplanes.

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Figure 2