Dakota Digital CMX operation manual Gain

CMX High Performance Material & Coating Thickness Gauge

7.4 Gain

The gain, or amplification of the return echoes, can be adjusted in the CMX to accommodate a variety of applications. The setting of the gain is crucial in order to obtain valid readings during the measurement process. Too much gain may result in erroneous measurements, by detecting on noise rather than the actual material back wall itself. Not enough gain may result in intermittent detection. It may also result in lack of detection on internal flaws, pits, or porosity. The gain can easily be compared to the volume control of a home stereo system. If you turn it up too muc h, you can’t hear the music clearly. If it’s turned down too much, you can’t hear it at all.

The CMX has three gain settings (VLOW, LOW, MED, HI, VHI). The gain range is 42dB – 50dB in 2dB increments. Note: The CMX has been optimized for the MED gain setting for all common applications. It should be operated in this mode as standard. However, some applications may require the lower or higher gain settings. When? The low settings may be necessary for noisy or granular cast materials. How do I know when to lower the gain? If the reading becomes sporadic and won’t settle down or resolve on a thickness value, the user can assume that the material is either very noisy aluminum, or granular cast iron. This would be a good time to change the CMX to lower gain setting and see if the reading settles down and become stable.

How do I know when to increase the gain? Often times the user will be trying to measure a material that is hard to penetrate or pass sound through. This may be due to the material type, or overall thickness of the material. When a material is hard to pass sound through because of the thickness or general make-up, it would be a good time to consider switching the CMX into a higher gain setting. Another example might be the need to i ncrease overall sensitivity for locating fine pits or flaws. In any case, the selectable gain settings offer the user some additional options to resolve and overcome application issues.

Note: When the echo-echo thru-paint measurement mode is selected, the manual

gain feature is disabled and grayed out in the menu items. In this mode, the CMX switches to an automatic gain mode (AGC) that optimizes the gain setting automatically in the hardware of the CMX.

The procedures to adjust the Gain are outlined below:

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