Chapter 3. Making Measurements
USM Go Operator’s Manual 87
3.9 Using TCG Mode (Optional)
When the optional TCG mode is in use, echoes from equally sized reflectors are shown at the same height on the A-Scan display. Before
using the TCG mode do the following:
1. Make sure that the instrument/probe combination has been properly calibrated and that all instrument settings (PULSER,
RECEIVER, etc.) have been properly configured. Changing these settings after the TCG reference points have been entered will affect
the accuracy of your measurements.
2. Up to 16 TCG points may be recorded, but a minimum of two points are required to define the curve. This process allows the
instrument to calculate and compensate for the effect of material depth on reflector echo height. Successive data points do not have to
progressively decrease in amplitude. That is, the DAC/TCG curve does not have to have a constantly descending slope.
3.9.1 Generating the TCG Reference Curve
TCG reference points are derived from the points used to create the DAC curve. Points are typically taken from a standard with equally
sized reflectors (holes) located at various material depths. The primary echo from each of these points, for a total of up to 16 echoes, are
recorded. When TCG is active, the instrument compensates for different material thickness by applying a varying gain level to echoes at
material depths other than the baseline depth.
Note: TCG reference points, curve, and status are stored with a data set. When recalled, curve status is the same as when it was stored.
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