3B37

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 3B37 is a single-channel signal conditioning module that

interfaces, amplifies and filters input voltages from a J, K, T, E, R,

S or B-type thermocouple and provides isolated simultaneous

voltage and current outputs linear with input voltage. 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. The current output

withstands 130 V rms without damage and interfaces user

equipment through screw terminals located on the 3B Series

backplane. This plug-in, mix-and-match, hot-swappable module

is easily field calibrated via front-panel zero and span

adjustments for both voltage and current outputs.

Accurate and System Ready – Internal cold-junction

compensation largely corrects errors arising from parasitic

thermocouples formed by thermocouple connection to the

generates a predictable upscale signal to indicate an open

thermocouple; for a downscale response, connect a 47MΩ, 0.25

Watt resistor across screw terminals 2 and 4 on the 3B Series

backplane

3B Series Custom Ranging Program – Externally-

programmable version Model 3B37-X-00, enable the user to

configure a special input range by using the optional plug-on

AC1310 ranging card, which houses user-supplied resistors to

determine zero and span. To facilitate selecting resistors, a

Windows program, 3B-Custom, calculates resistor values based

on the user-desired input/output ranges.

Inside the 3B37 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) or can be externally

programmed (Model 3B37-X-00) via user-supplied resistors

inserted in the optional AC1310 plug-on ranging card. Zero

suppression can exceed 100% of the input range. This enables

suppression of a zero-scale input value amny times larger that

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

users a proprietary modulation technique for linear, stable and

reliable performance. A demodulator on the computer side of

the signal transformer recovers the original signa, which is then

filtered and buffered to provide a low-noise, low-impedance

output voltage, this output also drives a voltage-to-current (V/I)

converter to provide a simultaneous current output for

interfacing versatility.

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Figure 2