3
Output Waveforms
De nitions
Count (N): For rotary motion, the number of bar and
window pairs or counts per revolution (CPR) of the code-
wheel. For linear motion, the number of bar and window
pairs per unit length (lines per inch [LPI] or lines per mm
[LPmm]).
One Cycle (C): 360 electrical degrees (°e), 1 bar and
window pair.
One Shaft Rotation: 360 mechanical degrees, N cycles
(rotary motion only).
Line Density: The number of re ective and non-re ec-
tive pairs per unit length, expressed as either lines per
inch (LPI) or lines per mm (LPmm).
Pulse Width (P): The number of electrical degrees that an
output is high during one cycle, nominally 180°e or 1/2
a cycle.
Pulse Width Error (ΔP): The deviation in electrical degrees
of the pulse width from its ideal value of 180°e.
State Width (S): The number of electrical degrees
between a transition in the output of channel A and the
neighboring transition in the output of channel B. There
are 4 states per cycle, each nominally 90°e.
State Width Error (ΔS): The deviation in electrical degrees
of each state width from its ideal value of 90°e.
Phase (φ): The number of electrical degrees between the
center of the high state on channel A and the center of
the high state on channel B. This value is nominally 90°e.
Phase Error (Δφ): The deviation in electrical degrees of
the phase from its ideal value of 90°e.
Direction of Rotation: When the codewheel or codestrip
moves in the direction from pin 1 to pin 4, as viewed
when looking down on the lenses, channel B will lead
channel A. If the codewheel or codestrip moves in the
opposite direction, channel A will lead channel B.
Optical Radius (Rop): For rotary motion, the distance
from the codewheel’s center of rotation to the center
line connecting the two lenses of the encoder.
Gap (G): The distance from the top of the package to the
surface of the re ective codewheel or codestrip.
Specular Re ectance (Rf ): a measure of a surface’s re ec-
tive nish. This is quanti ed by the amount of light re-
ected when hit with an incident beam. A device called a
scatterometer is used to quantify specular re ectance on
a percent scale. (Contact factory for more information.)
Radial and Tangential Misalignment Error (ER, ET): For
rotary motion, mechanical misalignment in the radial
and tangential directions relative to the codewheel.
Angular Misalignment Error (EA): angular misalignment
of the sensor in relation to the tangential direction. This
applies for both rotary and linear motion.
S1 S2 S3 S4 f
P
C
CH. B
CH. A
ALL FOUR STATES (S1 TO S4)
ARE MAINTAINED.
CODEWHEEL ROTATION OR LINEAR MOVEMENT
AMPLITUDE
HEDR-8000
SHAFT
CODEWHEEL
RADIAL
TANGENTIAL
HEDR-8000
SHAFT
CODEWHEEL
EA