HEDS-97E0R50 AVAGO [AVAGO TECHNOLOGIES LIMITED], HEDS-97E0R50 Datasheet - Page 2

• Manufacturer Part Number: HEDS-97E0R50
• Description: Small Optical Encoder Modules 200 LPI Analog Voltage Output
• Manufacturer: AVAGO [AVAGO TECHNOLOGIES LIMITED]

Theory of Operation
The HEDS-97EX is a C-shaped emitter/detector module.
Coupled with a codewheel/codestrip, it translates rotary
motion into a two-channel analog output.
The module contains a single Light Emitting Diode (LED)
as its light source. The light is collimated into a parallel
beam by means of a single lens located directly over the
LED. Opposite the emitter is the integrated detector
circuit. This IC consists of multiple sets of photodetectors
and the signal processing circuitry necessary to produce
the analog waveforms.
The codewheel/codestrip moves between the emitter
and detector, causing the light beam to be interrupted
by the pattern of spaces and bars on the codewheel/
codestrip.
The photodiodes, which detect these interruptions, are
arranged in a pattern that corresponds to the radius and
count density of the codewheel/codestrip.
These detectors are also spaced such that a light period
on one pair of detectors corresponds to a dark period on
the adjacent pairs of detectors. The photodiode outputs
are fed through the signal processing circuitry, which
produce the final outputs for Channel A and Channel
B. Due to this integrated phasing technique, the analog
output of Channel A is in quadrature with Channel B (90
degrees out of phase).
2
Definitions
Count (N): The number of bar and window pairs or counts
per revolution (CPR) of the codewheel. Or the number of
lines per inch of the codestrip (LPI)
1 shaft rotation = 360 degrees
1 cycle (c)
Direction of Rotation: When the codewheel rotates in the
counter-clockwise direction (as viewed from the encoder
end of the motor), channel A will lead channel B. If the
codewheel rotates in the clockwise direction, channel B
will lead channel A.
Line Density: The number of window and bar pair per
unit length, express in either lines per inch (LPI) or lines
per mm (LPmm)
Optical Radius (Rop): The distance from the codewheel’s
center of rotation to the optical center (O.C) of the
encoder module.
Gap (G): The distance from surface of the encoder to the
surface of codewheel or codestrip
Mounting Position (R
center of rotation to center of Alignment Tab receiving
hole.
Radial and Tangential Misalignment Error (E
rotary motion mechanical displacement in the radial and
tangential directions relative to the nominal alignment
Angular Misalignment Error (E
of the sensor in relation to then tangential direction.
This applies for both rotary and linear motion.of elec-
trical degrees that an output is high during one cycle,
nominally 180°e or 1/2 a cycle.
= N cycles
= 360 electrical degree, equivalent to 1
bar and window pair.
M
): Distance from Motor Shaft
A
): Angular misalignment
R
and E
r
): For