5B38

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 5B38 is a wide-bandwidth single-channel signal

conditioning module that interfaces, amplifies, and filters

signals from full-bridge and half-bridge strain-gage transducers

between 300Ω and 10kΩ. The module provides an isolated

bridge excitation of +10V and a protected, isolated precision

output of -5V to +5V. The 10 kHz bandwidth of the module

ideally suits to measure signals that vary rapidly with time, such

as strain on an automobile chassis during a crash test.

The 5B38 protects the computer side from damage due to field-

side over-voltage faults. The module withstands 240V rms at its

input terminals without damage, thereby shielding computer-

side circuitry from field-side over-voltage conditions. In

addition, the 5B38 is mix-and-match and hot-swappable with

all 5B Series modules, so can be inserted or removed from any

socket in the same backplane without disrupting system power.

The 5B38-04 contains bridge completion circuitry, so can

function with half-bridge strain gages. For quarter-bridge

requirements, the user must complete the bridge input to the

half-bridge level externally. The factory can configure the

module for a wide range of input ranges (sensitivities).

A signle-pole anti-aliasing filter resides at each modules input.

A three-pole, low-pass filter in the output stage sets the

bandwidth and yields optimal noise performance for accurate

measurement of small signals in high electrical noise. A

chopper-stabilized input amplifier provides low drift and stable

gain.

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. An

additional benefit, the output section acts as a third floating

port, eliminating possible problems from ground loops and

power-supply noise. The output common must be kept within

+3V 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