Allen-Bradley 845H Incremental Encoders – 845H-SJDZ24FWY2C

Technical Dossier

Product Details And Specifications

Allen-Bradley 845H Series Technical Notes

The Allen-Bradley 845H series is a heavy-duty incremental encoder line manufactured by Rockwell Automation, deployed across global heavy industry including petrochemical refineries, nuclear power facilities, steel mills, pulp and paper plants, and offshore drilling platforms. The 845H platform is engineered for high-resolution shaft position and velocity feedback in demanding environments where vibration, contamination, and extreme temperature cycles are routine operating conditions. Its widespread installed base — spanning decades of continuous production — makes it one of the most referenced encoder families in North American and Asia-Pacific industrial automation infrastructure.

The Evolution of 845H Architecture

The 845H series was introduced by Allen-Bradley (subsequently Rockwell Automation) as a successor to earlier 845 and 845T encoder families, addressing the need for higher PPR (pulses per revolution) resolution and improved environmental sealing. Early variants operated with single-ended TTL output and limited PPR options (up to 1024 PPR). Mid-generation models introduced differential line driver (RS-422) outputs, extending cable run capability to 300+ meters without signal degradation — a critical requirement in large-footprint process plants.

Later 845H configurations expanded PPR options to 5000 and beyond, added complementary output channels (A, B, Z with inverted pairs), and adopted IP67-rated housing with stainless steel shaft options for washdown and corrosive environments. The series is mechanically compatible with standard 58mm flange and servo-mount configurations, enabling direct replacement of legacy encoders without mechanical rework. As of 2026, the 845H series is in a mature/sustaining lifecycle phase; Rockwell Automation continues to supply replacement units and spare parts, but new system designs are increasingly directed toward the 842E (EtherNet/IP absolute encoder) platform. For facilities maintaining existing 845H-based motion control infrastructure, long-term maintenance sourcing remains the primary procurement driver.

845H Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked models within the Allen-Bradley 845H incremental encoder series. Each unit is a shaft-mount incremental encoder with differential line driver output unless otherwise noted.

845H-SJDZ24FWY2C: 2500 PPR, 5–26V DC, differential output, 5/8" shaft, IP67 housing, face mount flange
845H-SJDZ12FWY2C: 1024 PPR, 5–26V DC, differential line driver, 5/8" shaft, standard face mount
845H-SJDZ10FWY2C: 1000 PPR, 5–26V DC, differential output, 5/8" shaft, IP67 rated
845H-SJDZ05FWY2C: 500 PPR, 5–26V DC, differential line driver, 5/8" shaft, general industrial
845H-SJDZ25FWY2C: 2048 PPR, 5–26V DC, differential output, 5/8" shaft, face mount
845H-SJDZ50FWY2C: 5000 PPR, 5–26V DC, high-resolution differential output, 5/8" shaft
845H-SJDZ60FWY2C: 600 PPR, 5–26V DC, differential line driver, 5/8" shaft, IP67
845H-SJDZ36FWY2C: 3600 PPR, 5–26V DC, differential output, 5/8" shaft, servo mount
845H-SJDZ48FWY2C: 4096 PPR (binary), 5–26V DC, differential output, 5/8" shaft
845H-SJDZ20FWY2C: 2000 PPR, 5–26V DC, differential line driver, 5/8" shaft, face mount
845H-SJDZ15FWY2C: 1500 PPR, 5–26V DC, differential output, 5/8" shaft, IP67
845H-SJDZ08FWY2C: 800 PPR, 5–26V DC, differential line driver, 5/8" shaft
845H-SJDZ04FWY2C: 400 PPR, 5–26V DC, single/differential output, 5/8" shaft, general duty
845H-SJDZ02FWY2C: 200 PPR, 5–26V DC, differential output, 5/8" shaft, low-resolution feedback
845H-SJDZ01FWY2C: 100 PPR, 5–26V DC, differential line driver, 5/8" shaft, basic tachometer duty
845H-SJDZ30FWY2C: 3000 PPR, 5–26V DC, differential output, 5/8" shaft, high-cycle servo applications
845H-SJDZ16FWY2C: 1600 PPR, 5–26V DC, differential output, 5/8" shaft, IP67 rated

Quality Control for the 845H Range

Each 845H encoder processed by DriveKNMS undergoes a structured inspection and functional verification protocol prior to dispatch.

Mechanical Inspection: Shaft runout measurement (tolerance ≤0.025mm TIR), bearing play assessment, housing integrity check for IP67 seal condition, and connector/cable entry inspection for ingress damage.

Electrical Verification: Supply voltage range test (5V and 26V endpoints), output signal integrity check on all channels (A, B, Z and complements) using oscilloscope capture at rated RPM, differential output symmetry verification, and short-circuit protection confirmation.

PPR Accuracy Test: Pulse count verification against reference standard at defined RPM to confirm stated PPR accuracy within ±0.1% over full rotation.