HP 5501A Operating And Service Manual page 55

2.20 10780A Receiver
Each axis of the Laser Transducer System has a receiver with a lens photodiode assembly in
the front. I t must be positioned so that the polarizing vectors of the laser beam are parallel or
perpendicular to the line defined by the two mounting holes (within
+ 3 O )
as shown in Fig-
ure 2-28.
When mounting the receiver (see Figure 2-28) keep the following points in mind:
a. At a 4 5 O position the signal will go to zero.
b.
The receiver dissipates between 2 and 2.5 watts. Plastic pads keep an air gap around
the receiver and also acts as thermal and electrical isolators.
c.
Allow room for the cable to connect to the back connector of the receiver.
CAUTION
Use Nylon screw only (HP 2360-0369). The receiver housing
must be electrically isolated from mounting fixture.
BEAM DIAMETER
7.6 mm
BEAM
(.30)
,
L
SPACI NG
I
I
- - ,
12.7 mm
PHOTODETECTOR ('50)
INSULATING
,---.
I
-
9.9mm
(0.39)
TO AVOID GROUND LOOP
Figure 2-28. 70780A Receiver Dimensions
2.21 ACCURACY CONSIDERATIONS
To optimize the combined operation of the Laser Transducer System and the machine or
measuring system on which it is mounted, it is necessary that you understand the factors that
affect system accuracy. Only when
all
of these factors and their interrelationship is under-
stood is it possible to predict the performance of a system. A summary of the major factors
affecting accuracy are as follows:
a. Velocity of light compensation.
b. Deadpath error compensation.
c. Material temperature compensation.
d. Cosine error compensation.