Industrial 57C421B Pulse Tachometer Input Module

The Reliance 57C421B Pulsetach Input Module is a dedicated tachometer input interface for the AutoMax Multibus I/O family, designed to accumulate pulses from a photoelectric pulsetach and serve as the primary connection between a tachometer and the AutoMax/DCS 5000 control system. It supports single- or dual-channel pulsetach inputs with supply voltages from 5 to 12 V DC and provides three input channels (A, B, and Z) for phase A, phase B, and Z-pulse (origin/marker) signals, using an eight-resistor AutoMax programming scheme. Inside the module there are a 24-bit counter, a 24-bit comparator, and a 16-bit internal timer to enable high-resolution pulse counting and timing, with input frequency handling up to 150 kHz and isolation rated at 500 V RMS for safety. Typical applications include speed sensing and rotational measurement in Reliance AutoMax Multibus systems, where the Pulsetach input module acts as the core tachometer interface to the automation controller.