1. General Information

• Part Number: 57421, 57C421, 57421-2, 57C421B

• Manufacturer: Reliance Electric (Rockwell Automation / ABB / Baldor)

• Series: AutoMax DCS 5000 / Multibus I/O System

• Type: Pulse Tach Input Module (Encoder/Tachometer Interface)

• Application: Connects pulse tachometers/encoders to AutoMax; measures speed, direction, position (A/B/Z phases)

• Status: Obsolete; refurbished/used available

• Mounting: Standard AutoMax rack plug‑in (any slot)

  

2. Electrical Specifications

• Backplane Power: +5 VDC, ±12 VDC

• Input Signals: 3‑channel pulse (A‑phase, B‑phase, Z‑pulse for zero reference)

• Input Voltage: 5–12 VDC

• Max Input Frequency: 100 kHz

• Counter/Comparator: 24‑bit resolution

• Internal Timer: 16‑bit, 2 kHz

• Isolation: 500 Vrms (channel‑to‑backplane)

• Registers: 8 read/write registers for AutoMax tasks

• Power Consumption: ≤ 7 W

• Indicators: LEDs: CCLK OK, FORWARD, REVERSE, LATCH, CLEAR, COUNT STOP

• Jumpers: None (software‑configured)

3. Mechanical Data

• Dimensions (W×H×D): 31.8 × 187.3 × 38.1 mm (standard AutoMax)

• Weight: approx. 0.70 kg

• Construction: Conformal coated, industrial grade

• Connector: Rear gold finger; front 20‑pin female field connector

4. Environmental

• Operating Temp: 0 °C to +55 °C

• Storage Temp: −20 °C to +70 °C

• Humidity: 10%–90% RH, non‑condensing

• Certifications: UL, CSA, CE

5. Key Features

• High‑speed 100 kHz pulse input for tachometers/encoders

• 24‑bit precision counter for accurate speed/position tracking

• 3‑phase (A/B/Z) support for direction and zero‑position detection

• 500 Vrms isolation for noise immunity in heavy industry

• LED status diagnostics for quick troubleshooting

• Hot‑swap capable; no system shutdown for replacement

• No on‑board jumpers; all setup via software

6. Compatibility

• Racks: AutoMax 6‑slot / 10‑slot / 16‑slot

• CPU: 57407, 57C407 series

• I/O: 57401, 57405, 57406, 57410, 57411, 57412, 57419

• Replacement: 57421‑2 / 57C421 / 57C421B fully interchangeable