Series M21 Modular Incremental Encoders


Series M21 Modular Optical Encoder

 M21 Incremental Encoder
  Dynapar Brand Logo

Quick Specs...

  • Modular, Incremental Encoder for Stepper and Small Servo Motor Feedback
  • Phased Array Sensor Technology Provides High Temperature and Operating Frequency and Allows 0.020" (0.5 mm) of Axial Play
  • Resolutions to 2048 PPR with Index Standard; Optional 4, 6, 8 or 12 Pole Commutation Tracks for Brushless Servo Motors
  • Easy Installation and Removal without Special Tools or Parts

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Overview Industry/Application Specifications Related Info  

Overview / Design Principle:

Using industry standard package dimensions, the M21 is easily installed onto the motor without time-consuming adjustments or special tools. Its unique mechanical design automatically centers and gaps the disc during installation.

For Brushless DC (BLDC) servo control, optional 3 phase commutation tracks replace the traditional Hall Effect sensors. These optically-generated signals provide higher accuracy and reliability, improving the performance and reliability of the servo system.

Features and Benefits:

  • The M21 design operates up to 120°C. The high temperature plastics, phased array sensor, and low current requirements stabilize the output signals over a wide range of input voltage, ambient temperature, or output frequencies.
  • The M21 provides 30 degrees of adjustment to align the signal outputs to the shaft position. Using an industry standard Size 21 modular mounting pattern, the index mark on the disc hub can be coarse aligned to the index sensor position on the housing. The housing rotates to allow further adjustment of the index or fine alignment of the commutation channels to the BLDC motor windings.
  • The M21 enclosure is dirt-tight, rated NEMA 1 / IP50. The cover is gasketed to seal the disc and optics from contamination. Additionally, the base can be sealed to the motor for further environmental protection.
  • The M21 outputs are protected from short circuits, and operate on 5 or 12 VDC power.

The Dynapar Advantage:

  • Innovative, high quality leading edge technology encoder products
  • Broad commercial - industrial grade product line
  • Fast 3 Day Delivery and customized built to order solutions available
  • Global Manufacturing & Service Support
  • Fast-Friendly Customer Service & Technical Support with Multi-Lingual Capabilities
  • Global Network of Authorized Resellers
  • Competitive Product Warranty:  2 Years  


The Dynapar brand M21 modular encoder provides high-performance, cost effective feedback for stepper and servo motor controls.

Standard Operating Characteristics
Code: Incremental
Resolution: (pulses/revolution) Incremental: 500 to 2048 PPR
Commutation: 4, 6, 8 or 12 pole
Accuracy: Incremental: ±5 arc-mins. max. edge to edge;
Commutation: ±6 arc-mins. max.
Sense: (viewing encoder mounting surface) Incremental: A leads B by 90° for CCW rotation of motor shaft;
Commutation: U leads V, V leads W by 120° for CW rotation of motor shaft
Phasing: Incremental: 90° ± 18° electrical
Commutation: 8 Pole: 30°; 6 Pole: 40°; 4 Pole: 60° mechanical
Index to U Channel: ±1° mechanical - Index center to U channel edge
Symmetry: Incremental: 180° ± 18° electrical
Commutation: 8 Pole: 45°; 6 Pole: 60°; 4 Pole: 90° mechanical
Index Pulse Width: 180° ± 36° electrical (gated with B low) standard

Input Power Requirements: Incremental: 5 or 12 VDC ± 10% at 100 mA max. (excluding output load);
Commutation: 5 or 12 VDC ± 10% at 75 mA max.(excluding output load)
Output Signals: 7272 Line Driver: 40 mA sink/source max.;
Open Collector w/2.0 kO pull-ups: 16 mA sink max.
Frequency Response: 200 kHz min.
Termination: Connector: PCB mounted dual row head with 0.1" x 0.1" pin spacing, 10 pins (incremental only), 16 pins (w/commutation);
Cable: conductors - 28 AWG, stranded (7/36), insulation - black, PVC;
Shield: aluminum/polyester foil plus tinned, copper drain wire (28 AWG, 7/36)
Noise Immunity: Conforms to EN50082-1 Light Industrial for Electro-Static Discharge, Radio Frequency Interference, Electrical Fast Transients, Conducted Interference, and Magnetic Fields (for models or applications with shielded cable)

Weight: Connector: 1 oz. (28 gm) typ.
Connector w/cover: 1.5 oz. (43 gm) typ.
Cable: 2.5 oz (71 gm) typ.
Cable w/cover: 3 oz. (85 gm) typ.
Dimensions: Outside Diameter: 2.1" (53 mm) max. w/cover, 2.0" (51 mm) max. without cover;
Height: 0.8" (20.3 mm) max. (w/cover, excluding connector);
Emitter to Detector Gap: 0.070" (1.8 mm) min.
Material: Base, Housing, & Cover: high temperature, glass filled polymer;
Hub: Aluminum;
Disk: 0.030" thick glass
Finish: Base & Housing: black;
Cover: RAL 7010 (dark grey)
Moment of Inertia: 6.64 x 10-5 in-oz-sec.2 (4.7 gm-cm2)
Hub Diameters: 1/4", 3/8", 7/16", 1/2", 6 mm, 8 mm, 10 mm, 12 mm nominal
Hub Dia. Tolerance: +0.001"/-0.000" (+0.026 mm/-0.000 mm)
Mating Shaft Length: 0.45" (12 mm) min. blind hub clamp screw, 0.65" (16.5 mm) exposed hub clamp screw; 0.75" (19 mm) max. inside cover
Mating Shaft Runout: 0.002" (0.05 mm) max. (Includes shaft perpendicularity to mounting surface)
Mating Shaft Endplay: +0.005"/-0.015" (+0.13 mm/-0.38 mm) nominal ("+" indicates away from mounting face)
Mounting: Base: (2) #4-40 (M2.5) #1 Phillips fillister head cap screw on 1.812" (46 mm) B.C., 0.01" (0.254 mm) true position to shaft;
Shaft: split hub w/collar clamp, #2-56 hex socket cap screw (5/64" hex wrench included)
Electrical/Mechanical Alignment Range: ±15° mechanical
Acceleration: 100,000 rad/sec.2 max.
Velocity: 12,000 RPM max.

Operating Temperature: -40° to 120°C
Storage Temperature: -40° to 85°C
Shock: 50 G's for 11 msec duration
Vibration: 2.5 G's at 5 to 2000 Hz
Relative Humidity: 90% non-condensing
Enclosure Rating: NEMA 1 / IP50 dirt-tight (for models with cover)

Available Specifications:

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