Isolated analog signal conditioner

The 8B43 analog signal conditioner by Dataforth includes 10 modules and has a special input circuit that provides protections against accidental connection of power-line voltages up to 240 V AC.

August 9, 2012

Dataforth’s isolated analog signal conditioner, the 8B43, interfaces to dc linear voltage displacement transducers (LVDT) which operate on a 1 0V excitation voltage and up to 2 0mA of  excitation current.

The 8B43 family includes 10 different modules with input ranges from -1 V to +1 V through -5 V to +5 V. Each module isolates, filters, and amplifies a voltage input signal, then provides an analog voltage output.

Specific 8B43 DC LVDT applications have included measuring soil sample deformation under load to determine soil strength, controlling pill weight and thickness in making tablets from medicinal powder, continuously monitoring fluid levels as part of a leak detection system (using a hydraulic oil compatible module) and replacing limit switches to ensure higher resolution on bottle inspection machinery.

Signal filtering in the 8B43 is achieved with a 5-pole filter that is optimized for time and frequency response and provides 100 dB per decade of normal-mode rejection above 1 kHz. One pole of the filter is on the field side of the isolation barrier for anti-aliasing;  the other four are on the system side.

A special input circuit provides protection against accidental connection of power-line voltages up to 240 V ac, while clamp circuits on the I/O and power terminals protect against harmful transients. Isolation is provided by transformer coupling to suppress transmission of common mode spikes or surges. The module is powered from +5 V dc, ±5%.

Designed for installation in Class I, Division 2, hazardous locations, the 8B43 offers a high level of immunity to environmental noise.


– Edited by Chris Vavra, Control Engineering,