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4 <br />Another way to calculate the amplitude at 80$ bond is by <br />plotting these same log readings on a semi-log.chart. <br />Plot the values for 0$ Bond and 100$ Bond vs. their <br />respective Amplitudes on a semi-log chart - amplitudes on <br />the log scale (y-axis), and bond indices on the linear scale <br />(x-axis). Then, connect the points with a straight line. <br />To estimate the amplitude corresponding to an 80$ Bond <br />Index, enter the graph on the x-axis at 80$ bond. Draw a <br />straight line upward until you reach the diagonal line <br />connecting the 0$ and 100$ points. Continue by drawing a <br />horizontal line to the y-axis. This point on the y-axis is <br />the amplitude corresponding to an 80$ Bond Index. <br />Using the values from the example above, your chart will <br />look like that shown below: <br />,W <br />w <br />A <br />b <br />.0 <br />b <br />70 <br />0% BOND <br />n B1 mV <br />> : 100% BOND <br />E ' <br />v : 1 mV <br />s <br />W <br />O , <br />F- ~ <br />J 2.4 mV <br />Q <br />Q <br />.~ <br />'' 80% BOND <br />a <br />.~ <br />a e a z .o w m ~o n o v <br />% BOND <br />In this example, 80$ bond shows an amplitude of 2.4 mV. <br />A convenient way to evaluate the log is to draw a line on <br />the bond log's amplified amplitude (5X) track corresponding <br />to the calculated 80$ bond amplitude. Whenever the logged <br />amplified amplitude (5X) curve drops below (to the left of) <br />the drawn line; this indicates a bond of 80$ or more. <br />