Appendix B
5B Series Module Data Sheets
SC-2311 User Manual
B-34
ni.com
5B40/5B41 Isolated, Wide Bandwidth Millivolt and
Voltage Input
Functional Description
The 5B40 and 5B41 are wide-bandwidth
single-channel signal conditioning modules that
amplify, protect, filter and isolate analog input
voltages. Both modules provide a 10 kHz
bandwidth which ideally suits them to measuring
signals that vary rapidly with time. Examples
include pressure inside a plastic injection molding
machine, strain on an automobile chassis during a
crash test and vibrations on a machine bearing
shortly before failure.
The 5B40 and 5B41 protect the computer side from damage due to field-side overvoltage
faults. All models withstand 240 V rms at their input terminals without damage thereby
shielding computer-side circuitry from field-side overvoltage conditions. In addition, 5B40
and 5B41 Series modules are mix-and-match and hot swappable, so can be inserted or
removed from any socket in the same
backplane
without disrupting system power.
Inside 5B40/5B41 Modules
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.
A single-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.
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 Vdc of power common.
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