Spectrum 1746sc-CTR4, Owner'S Manual, Page: 23 / 66

Chapter 3: Things To Consider Before Using Your Module
23
Note: The X1 Quadrature mode provides additional Anti-Jitter
circuitry. This distinguishes between a valid quadrature sequence
and an invalid sequence due to electrical noise or jitter. Jitter can
occur if a quadrature encoder stops rotating right at an input sensor
trip point. This can cause additional unwanted clock pulses. The X1
quadrature mode can detect invalid transitions and filter these out.
X4 Quadrature Encoder
Like the X1 quadrature encoder, the count direction is determined by the
phase angle between inputs A and B. If A leads B, the counter
increments. If B leads A, the counter decrements. However, the counter
changes value on the rising and falling edges of inputs A and B. The
counter increments four times per quadrature cycle.
Note: In the X4 Quadrature mode, invalid signals are not detected. A
broken input wire, jitter or noise on the input can cause additional
counts to be registered. The modules response to four possible error
conditions are listed below:
Input A is active while input B is stuck high: Module will count down on input A transitions.
Input A is active while input B is stuck low: Module will count down on input A transitions.
Input A is stuck high while input B active: Module will count down on input B transitions.
Input A is stuck low while input B is active: Module will count up on input B transitions.
B
Forward Rotation Reverse Rotation
A
Input A
Input B
Quadrature
Encoder
B
A
x1 Count
x4 Count
1
2
3
2
1 0
1 2 3 4 5 6 7 8 9 10 11 12 11 10 9 8 7 6 5 4 3 2 1 0