HP 5501A Operating And Service Manual page 58

2.24 Material Temperature Compensation
2.25 THERMAL EXPANSION OF THE PART. The previous section discussed compensation
to eliminate errors due to a change in the laser wavelength. I n addition, it is necessary to
compensate for the expansion or contraction of the material of the part being machined or
measured a s the temperature changes. Strictly speaking, this problem is not related to the
Laser Transducer System and occurs regardless of the position sensing transducer used on
the machine. It is, however, of such prime importance that it must be understood by the user
if
he wishes to obtain optimum machine performance. Figure 2-30 shows the relative effect
of different errors.
600 I I I
I
I I I I
MATERIAL TEMPERATURE ERROR OF l o C. (STEEL)
500
--
400
--
300
--
200
--
AIR TEMPERATURE ERROR OF l o C.
100
--
AIR PRESSURE ERROR OF 5 mm Hg
-
0 10 20 30 40 50
MEASURED DISTANCE (Metres)
Figure 2-30. Relative Effect of Errors in Atmospheric and Material Temperature Factors