7b37-j-10-2 Analog Devices, Inc., 7b37-j-10-2 Datasheet - Page 2

• Manufacturer Part Number: 7b37-j-10-2
• Description: Isolated, Thermocouple Input
• Manufacturer: Analog Devices, Inc.

GENERAL DESCRIPTION
The 7B37 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 an isolated and
protected precision output of either +1 V to +5 V or 0 V to +10
V, 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 rms 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. Rated to operate with a nominal +24
VDC supply, Model 7B37 is mix-and-match and hot-swappable
with other 7B Series input modules, so it can be inserted or
removed from any socket in the same backplane without
disturbing system power.
The three input pins of Model 7b37 are fully protected up to
120 V rms line voltages. A one-pole 3 Hz filter preconditions
the thermocouple signal prior to amplification, provided by a
low drift input amplifier. Cold junction compensation (CJC) is
implemented using a thermistor temperature sensor embedded
under the input screw terminal block on a 7B Series backplane.
A voltage reference source acts to offset the thermocouple
signal in accordance with the specified lower bound on the
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Figure 2
input temperature range. A current source provides the upscale
open circuit indication. Amplitude modulation is used to
implement transformer isolation (1500 V rms input-to-output
and power). Isolated front-end circuitry power is supplied by a
DC/DC converter. The output section contains a demodulator, a
two-pole low pass filter (-3 dB @ 3Hz), a buffer amplifier and a
power oscillator. The two-pole output filter and subsequent
buffer ensures that a low noise, low impedance (<1Ω) signal is
available at the output to drive loads to 2kΩ minimum.
7B37