DeFelsko PosiTector UTG v.3.0 Quick Guide - Manual (Page 7)

Cal Settings Menu Cal Settings Menu
The PosiTector UTG is factory calibrated. But in order for it to take
accurate thickness measurements of a particular material it must
be set to the correct sound velocity for that material. Be aware that
material composition (and thus its sound velocity) can vary from
stated tables and even between lots from a manufacturer.
Adjustment to a sample of known thickness of the material to be
measured ensures that the Gage is adjusted as close as possible
to the sound velocity of that specific material. Samples should be
flat, smooth and as thick as the maximum expected thickness of
the piece to be tested.
The PosiTector UTG allows four simple adjustment choices. All
four methods are based on the simple premise of adjusting the
sound velocity. The first three adjustment methods make 1-point
calibration adjustments to optimize the linearity of the PosiTector
UTG over small ranges. The fourth method makes a 2-point
calibration adjustment to allow for greater accuracy over a large
range.
Zero
PosiTector UTG probes can be "zeroed" to compensate for tem-
perature and wear. This action is not required when operating in
multiple-echo mode (UTG M probes only) except when the instru-
ment is new and after a Reset (pg. 8). However it ensures best
accuracy when operating in SE (single-echo) mode. Therefore it is
a good idea to "zero" the probe before each work shift and when
the temperature of the part changes. During zeroing, it does not
matter what the current velocity setting is.
1. Make sure the instrument is on and the probe is wiped clean.
2. Apply a single drop of couplant onto the zero plate located on
the underside of the probe connector. DO NOT apply couplant
directly onto the probe face.
3. Select the Zero menu option and follow the on-screen prompts.
Calibration Adjustment
6