DAKOTA ULTRASONICS DFX-7 Operation Manual
Also see for DFX-7: Operation manualManual
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Contents
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61CHAPTER EIGHTDISTANCE AMPLITUDE CORRECTION (DAC)8.1 Introduction to DACA DAC curve is a gate with a variable threshold to compensate for a given reflectortype and size measured at different depths. Unlike a standard gate, which typicallyhas a fixed threshold level regardless of the depth, the DAC curve is morerepresentative of the reflector size at different depths. In order to generate a DACcurve, calibration standards must made with the same material being inspected, therepresentative reflector size, and over a given thickness range. The DAC curve isthen used as an alarm to inform the user about the size of any given reflector at anydepth during the inspection process.Once the DAC curve has been established, the user can display; -2dB, -6dB, -10dB,-12dB, -6/-12dB, -6/-14dB, DAC or GATE at any time. The initial DAC curvegenerated is always displayed in conjunction with any of the above CURVE options.Additionally, the alarm can be set to TRIGGER on any of the curve options displayed.Therefore, if the -6/-12dB curve option has been selected, the user can toggle theTRIGGER options: GATE, DAC, -6dB, or -12dB.Note: Based on the screen resolution of the DFX-7, the dynamic range of the DACis approximately 18dB. As a result, inspection of any materials that attenuate morethan 18dB over the inspection range, the DAC feature should not be used, and TCG(Time Corrected Gain) should optionally be considered.8.2 Additional CommentsPrior to proceeding onto the next section to create a DAC curve, a few additionalitems will help with the users selection process in the menu items: Up to 8 points can be used to generate a DAC curve. 3 or more points must be used in order to draw a DAC curve. All the DAC curve or gate combinations only detect when the amplitude of thesignal is ‘at’ or ‘above’ the selected trigger option. Any of the DAC curves or gate displayed, can be set as the trigger alarmoption. The measure (meas) options are as follows:dB –%DAC – At the DAC curve represents 100%. Any signal generating anamplitude below the DAC curve is less than 100%, and any abovegreater than 100%. |
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