HEDS-5120-A02 HP [Agilent(Hewlett-Packard)], HEDS-5120-A02 Datasheet - Page 2

• Manufacturer Part Number: HEDS-5120-A02
• Description: High Temperature 125 Degree Celcious Two Channel Optical Incremental Encoder Modules
• Manufacturer: HP [Agilent(Hewlett-Packard)]

Standard resolutions for the
HEDT-9000 are 500 CPR and
1000 CPR for use with a HEDS-
6100 codewheel or equivalent.
For the HEDT-9100, standard
resolutions between 96 CPR and
512 CPR are available for use
with a HEDS-5120 codewheel or
equivalent.
Applications
The HEDT-9000 and 9100
provide sophisticated motion
detection at a low cost, at
temperatures to 125 C, making
them ideal for high volume
automotive applications.
Note: Agilent Technologies
encoders are not recommended
for use in safety critical
applications. Eg. ABS braking
systems, power steering, life
support systems and critical care
medical equipment. Please
contact sales representative if
more clarification is needed.
Theory of Operation
The HEDT-9000 and 9100 are C-
shaped emitter/detector modules.
Coupled with a codewheel, they
translate the rotary motion of a
shaft into a two-channel digital
output.
As seen in the block diagram,
each 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 polyetherimide
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
product the digital waveforms.
The codewheel rotates between
the emitter and detector, causing
the light beam to be interrupted
Block Diagram
Output Waveforms
by the pattern of spaces and bars
on the codewheel. The
photodiodes which detect these
interruptions are arranged in a
pattern that corresponds to the
radius and design of the code-
wheel. These detectors are also
spaced such that a light period on
one pair of detectors corresponds
to a dark period on the adjacent
pair of detectors. The photodiode
outputs are then fed through the
2
signal processing circuitry
resulting in A, A, B, and B. Two
comparators receive these signals
and produce the final outputs for
channels A and B. Due to this
integrated phasing technique, the
digital output of channel A is in
quadrature with that of channel B
(90 degrees out of phase).
Definitions
Count (N): The number of bar
and window pairs or counts per
revolution (CPR) of the
codewheel.