5B37
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 @
+25
o
C ambient temperature. The module generates a
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
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