7B14

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 7B14 is a low cost, single-channel signal conditioning

module that interfaces, amplifies and filters input voltages from

a wide variety of two-and three-wire platinum, copper and

nickel Resistor Temperature Detectors (RTDs) and provides a

precision output of either +1 V to +5 V or 0 V to +10 V, linear

with temperature. Model 7B14 features a nonlinearity of +0.05%

maximum (Pt and Cu RTDs). RTD excitation current, three-

wire lead resistance compensation and a predictable upscale

open circuit indication provide a complete signal conditioning

solution. Rated to operate with a nominal +24 VDC supply,

Model 7B14 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 7B14 are fully protected up to

+30 VDC. A 250 uA excitation current for platinum and nickel

RTDs and a 1mA excitation current for copper RTDs is

provided to create an input voltage to the 7B14. This current

also provides the upscale open circuit indication. A one-pole 3

Hz filter preconditions the RTD signal prior to amplification,

provided by a low drift input amplifier. The output section

contains a two-pole low pass filter (-3 dB @ 3 Hz) and a buffer

amplifier. The two-pole output filter and subsequent buffer

ensure that a low noise, low impedance (<1Ω) signal is available

at the output to drive loads to 2 kΩ minimum.

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Figure 2