Starrett SR200 Surface Roughness Tester - Manual (Page 28)

Chapter 7
Maintenance Calibration
Reference Standard
The sensitivity of the instrument is checked with the reference specimen supplied. This
comprises a ruled surface having an Ra value accurate to within 4% of the value marked on its
mount.
To provide confidence in results, it is recommended that a sensitivity check is made at the
beginning of each shift.
Sensitivity Check and Adjustment
The procedure for checking and adjusting the pick-up sensitivity is as follows:
1. Place the reference specimen on a flat surface and set up the instrument to make a traverse
across it. Make sure that the traverse unit body is parallel to the surface of the standard and
that the stylus traverses at right angles to the lay of the grooves.
2. Select the 0.8mm or 0.03in cut-off and the Ra parameter.
3. Make a measurement of the reference specimen and compare the Ra value from the display
with that marked on the specimen.
4. If it differs by more than 2% use the small screwdriver to turn the sensitivity adjuster. This is
located through the hole which is located in the front panel of the Display Unit, just above the
pick-up connector.
5. Repeat the measurement and adjustment, until the measured value is within 2% of the value
marked on the specimen.
Cleaning the Stylus
Occasionally clean the stylus with a camel hair brush moistened with a proprietary cleaning
agent.
Pick-up Skid
To reduce the effect of wear, on pick-ups with a rotatable skid, occasionally turn the skid round
to present a new contact surface. The skid is clamped by the screw in the front of the pick-up.
When loosening this screw, take care not to let the retaining pin next to the skid fall out. When
retightening the screw, ensure that the end cover is correctly positioned with respect o the
stylus and that the stylus is free to move.
7.1 Form 965 - SR200 4/11 2.5C/T starrett.com