3B30 / 3B31

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

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.

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.

assures stable long-term stability. At the amplifier input, a stable,

zero-scale input voltage is subtracted from the input signal to

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.

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.

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Figure 2