GE WESDAC D20A Analog Scan Module

The GE Fanuc WESDAC D20A, also cataloged as the D20A Analog Scan Module, operates as a dedicated hardware component for converting physical analog sensor variables into digital data registers within WESDAC industrial automation platforms.

Hardware Specifications

GE Fanuc Industrial Control and Signal Processing

• Channel-to-Channel Isolation Matrix: The D20A module incorporates internal galvanic isolation barriers between the external 32 analog inputs and the internal logic processing components. This layout isolates high-voltage ground spikes and common-mode noise on individual field lines, keeping raw electrical transients from bleeding into adjacent registers.
• Cold Junction Compensation (CJC): When interfacing with millivolt or current loops routed through detachable terminal blocks, the hardware runs continuous ambient thermal tracking routines. This internal compensation step stabilizes signal calibration drift caused by temperature swings in the surrounding panel enclosure, ensuring precise analog-to-digital conversion factors across all 32 channels.

Frequently Asked Questions

Q: Can the detachable terminal units of the D20A module be removed while the analog loops are under active load?

A: Yes, the physical separation of the front-facing terminal blocks is designed to support offline field service without disturbing the main rack backplane. However, uncoupling the terminal block during an active loop scan will instantly break the current loops, causing upstream instrumentation tracking faults and injecting zero-scale values into the local DNP3 database registers.

Q: How does the module handle a combination of both voltage and current signals across its 32 input channels?

A: The input circuitry uses hardware-selectable jumpers or dip-switch arrays located on the internal printed circuit board to establish individual channel parameters. For current signals (e.g., 4-20 mA), configuring the jumper introduces a precision low-impedance shunt resistor across the terminal inputs to drop the current loop down to a measurable voltage potential before A/D processing.