Allen-Bradley SST-PFB-SLC Encoders

Configured for precise shaft angular position and speed measurement in industrial control networks, the Allen-Bradley 845T-HC12PFW-1 (845T-HC12PFW) Optical Rotary Encoder provides direct physical/electrical execution. The heavy-duty encoder converts rotational mechanical motion into dual-channel quadrature digital signals via a 1024 PPR optical disk, delivering 5 VDC Differential Line Driver (DLD) outputs over a 1-meter pigtail cable.

Hardware Specifications

I/O Density Scaling & Deterministic Motion Control

The 845T-HC12PFW-1 interfaces with high-speed counter cards and drive feedback loops to support I/O density scaling and deterministic motion execution within Allen-Bradley Logix platforms. Differential line driver channels (A, B, and inverse signals) transmit high-frequency quadrature pulses that maintain high signal-to-noise ratios over extended cable runs. This high-density feedback architecture enables PLC and drive modules to execute closed-loop velocity calculation and position tracking without phase distortion or signal loss.

Frequently Asked Questions

Q: Can the 845T-HC12PFW-1 5 VDC line driver output be wired directly to a 24 VDC PLC input card?

A: No, connecting 5 VDC Differential Line Driver outputs to a 24 VDC input module will result in signal failure or channel damage. A 5 VDC to 24 VDC level converter card or a compatible 5 VDC differential counter module must be used.

Q: How are cable shield terminations handled to prevent noise on quadrature channels A and B?

A: The pigtail cable shield must be grounded at a single point at the receiving control cabinet earth ground bus. The shield should remain isolated and ungrounded at the encoder housing to prevent ground loop currents from interfering with pulse transmission.

Field Installation Guidelines

1. Mount the encoder using the integrated servo face mounting holes, ensuring proper alignment with the driving shaft to minimize radial and axial shaft loading.
2. Connect the 1/4-inch shaft to the target drive using a flexible shaft coupling; direct rigid coupling creates excessive bearing load and shortens mechanical operating life.
3. Route the 1-meter pigtail cable through dedicated low-voltage instrument raceways, keeping it separated from high-voltage AC motor lines by at least 200 mm.
4. Connect the pigtail wires according to the differential line driver pinout map, verifying 5 VDC supply voltage polarity before powering the system.
5. Ensure the encoder body is mechanically grounded to the machine frame and that all conduit connections meet site dust and liquid ingress specifications.