DMTA-10022-01EN, Rev. C, January 2015Chapter 10174Figure 10-8 The TDG zones and parametersThe TDG curve can be used to optimize near-surface resolution while providing ahigher maximum gain for thicker samples. You can also use the TDG curve inmeasurements of highly scattering materials, such as cast metals and fiberglass, inorder to minimize detection of scattered echoes occurring ahead of the back-wallecho.10.6.1 Maximum GainThe maximum gain indicates the maximum (time-dependent) receiver gain possible.The maximum gain is used to amplify echoes that are further out in time. In general,for any given application, the maximum gain should be set high enough that allechoes of interest are detected.The maximum available receiver gain can be adjusted from 0.0 dB to 99.0 dB. Whenno echo is detected (LOS prompt), the gain rises to the maximum level set by theinitial gain, slope, and maximum gain. When the maximum gain is set too high, thegage may hang up on transducer noise or other spurious signals; when it is set toolow, returning echoes may not be high enough for detection.The max gain can never be lower than the initial gain, and has a maximum value of99.0 dB.Time-dependent gaincurveINIT GAIN level zoneMB BLANKMAX GAINlevel zoneTDG SLOPE zone
