What is meant by Rotary Incremental Encoder Index Pulse “gating”? June 11, 2014

Quantum Devices Optical Encoder

Gating refers to the width of the Z (index) pulse relative to the A and B channels. With ungated devices the edges of the Z pulse have no hard relation to A & B.

Gating to channel A, requires the Z pulse to be high once per revolution and only when A is high.

Gating to channels A&B high requires the Z pulse to be high once per revolution and only when A AND B are high.

Gating to A creates a Z pulse roughly 180 Electrical Degrees in duration while gating to A&B creates a Z pulse roughly 90 Electrical Degrees in duration.

Gating to a smaller duration increases the precision of the Z pulse, but also requires the motion system to be able to read the Z channel at a faster rate.

Gating is sometimes required by certain drive/amplifier/controller manufacturers.

QD145 Z (Index Pulse) Specifications:

Ungated Z
Z-A/A-Z min = 0 Electrical Degrees
Z-A/A-Z max= 225 Electrical Degrees
Z width min = 180 Electrical Degrees
Z width Max = 540 Electrical Degrees

Z Gated to A
Z width min = 135 Electrical Degrees
Z with max = A true

Z Gated to A&B
Z width min = 45 Electrical Degrees
Z width Max = A&B true

Ungated Z
Z true over A&B> 45 Electrical Degrees
Z-A&B/A&B-Z min = 0 Electrical Degrees
Z-A&B/A&B-Z max= 315 Electrical Degrees
Z width min = 180 Electrical Degrees
Z width Max = 540 Electrical Degrees

Z Gated to A
Z width min = 135 Electrical Degrees
Z with max = A true

Z Gated to A&B
Z width min = 45 Electrical Degrees
Z width Max = A&B true

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Tags:  Encoder, Incremental Encoder, Absolute Encoder, Single-Ended Encoder, Differential Encoder, Servo2Go, Quantum Devices