DeFelsko PosiTector SPG Manuel D'instructions page 5

Additionally, the PosiTector body accepts a wide variety of
probe types including magnetic, eddy current, and ultrasonic
coating thickness, surface profile, environmental, hardness, salt
contamination, gloss, and ultrasonic wall thickness probes.
See www.defelsko.com/probes
Calibration & Verification of Accuracy
Calibration
Instrument calibration is typically performed by the manufacturer.
All probes include a Certificate of Calibration.
Verification of Accuracy
Instrument accuracy is verified using the included metal shim and
glass zero plate. Ensure that the glass plate and shim are clean
and dirt free before use.
Place the plate onto a stable, flat surface. Take several
measurements. If the average is greater than ±5 µm (0.2 mil),
Zero (pg. 4) the Gage.
Next, place the metal shim over the glass plate and measure,
ensuring the probe needle touches the glass plate in the area
between the shim's "legs". The average of several measurements
should be within the combined tolerances of both the Gage and
the shim.
If not, see Returning for Service (pg. 11).
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