Product Overview
The Allen-Bradley 845H-SJDZ24FWY2C is a Bulletin 845H Size 25 optical incremental encoder from Rockwell Automation, engineered to deliver precise speed, position, and direction feedback in demanding industrial motion control applications. The 845H-SJDZ24FWY2C converts mechanical shaft rotation into digital quadrature pulse signals, providing critical feedback data to servo drives, variable frequency drives, and PLC-based motion controllers. With its robust construction and high-resolution optical sensing, this encoder serves as a reliable feedback element in systems where positioning accuracy directly impacts production quality and throughput .
The 845H-SJDZ24FWY2C features a 1024 pulses-per-revolution (PPR) code disk with quadrature A and B channels plus a gated zero index (Z) channel. The A and B channels are phase-shifted by 90 degrees, enabling connected controllers to determine both the magnitude and direction of shaft rotation. The Z channel generates one pulse per revolution, providing a repeatable reference position for machine homing, indexing, and synchronization functions. This three-channel configuration makes the 845H-SJDZ24FWY2C suitable for applications requiring both incremental position tracking and absolute reference establishment .
The electrical interface of the 845H-SJDZ24FWY2C uses a differential line driver output compliant with RS-422 specifications, delivering complementary signals (A, /A, B, /B, Z, /Z) that provide superior noise immunity compared to single-ended output types. This differential signaling enables reliable data transmission over longer cable runs and in electrically noisy environments such as those found near motor drives, welding equipment, and high-power switching devices. The encoder operates from an 8-24 VDC unregulated power supply and supports frequency response up to 210 kHz, making the 845H-SJDZ24FWY2C capable of tracking high-speed rotation with accuracy .
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Series | Bulletin 845H, Size 25 |
| Product Type | Optical Incremental Encoder |
| Resolution | 1024 PPR (Pulses Per Revolution) |
| Output Channels | A, /A, B, /B, Z, /Z (Quadrature + Complementary + Zero Index) |
| Quadrature Phase Shift | 90° ±22°; Channel A leads B CCW |
| Symmetry | 50% ±10% |
| Zero Index | Gated 1/2 cycle |
| Output Type | Differential Line Driver, 5 VDC RS-422 |
| Output Drive Capability | ±20 mA |
| Power Supply | 8–24 VDC Unregulated |
| Frequency Response | 210 kHz (Data and Zero Index) |
| Maximum Operating Speed | 6000 RPM |
| Shaft Diameter | 3/8 inch (9.517 mm) |
| Shaft Loading – Axial | 89 N (20 lb) |
| Shaft Loading – Radial | 178 N (40 lb) |
| Mounting Configuration | Square Flange |
| Connection Type | Radial Connector (Side), with Mating Connector |
| Housing Rating | NEMA Type 4, 13; IP66 (IEC 529) |
| Operating Temperature | 0°C to +60°C |
| Storage Temperature | -25°C to +90°C |
| Shock | 50 g (11 ms duration) |
| Vibration | 20 g (4 to 2000 Hz) |
| Starting Torque | 2.5 Ncm typical |
| Moment of Inertia | 15 g·cm² |