5B37

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 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 +5V.

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 +0.25oC @

predictable upscale signal to indicate an open thermocouple, for

a downscale response, connect a 47MΩ, 0.25 W resistor across

screw terminals 1 and 3.

The 5B37 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 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.

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 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.

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..

.

.

Figure 2