3B30 / 3B31
GENERAL DESCRIPTION
set the zero-scale value. Zero suppression can exceed 100% of
the input range. This is ideal fro expanded-scale applications
requiring high-resolution measurement of a selected portion of
an input signal. For users convenience, the zero and span can be
factory configured to meet custom range needs (Models 3B30-
CUSTOM and 3B31-CUSTOM) or can be externally
programmed (Models 3B30-00 and 3B31-00) via user supplied
resistors inserted in the optional AC1310 plug-on ranging card.
Internal low-pass filtering with a 4Hz cutoff (-3dB) two-pole
Butterworth filter enhances both 60dB normal-mode and 160
dB common-mode rejection at 50/60 Hz, enabling accurate
measurement of small signals in high electrical noise.
The 3B30 & 3B31 are narrow-bandwidth (3Hz) single-channel
signal conditioning modules which amplify, isolate, filter and
protect analog input voltages and provide simultaneous
precision voltage and current outputs. Each module performs
complete signal conditioning, including isolating (+1500V peak
input-to-output and power) and protecting their computer side
outputs from damage and loss of signal integrity, and shielding
their inputs from damage from field-side over-voltage faults up
to 220V rms. The current output withstands 130V rms without
damage and interfaces user equipment through screw terminals
located on the 3B Series backplane. Each 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.
Signal isolation is accomplished by transformer coupling with 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 voltage; this
output also drives a voltage-to-current (V/I) converter to
provide a simultaneous current output for interfacing versatility.
3B Series Custom-Ranging Program – Externally-
programmable Models 3B30-00 and 3B31-00, 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.
A chopper-stabilized low-drift (+1uV/oC) input amplifier
assures stable long-term stability. At the amplifier input, a stable,
zero-scale input voltage is subtracted from the input signal to
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Figure 2
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