Checkline TI-CMX - Manual (Page 22)

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7.4 Gain
The gain, or amplification of the return echoes, can be adjusted in the TI-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 vol-
ume control of a home stereo system. If you turn it up too much, you can’t hear the
music clearly. If it’s turned down too much, you can’t hear it at all.
The TI-CMX has five gain settings (VLOW, LOW, MED, HI, VHI). The gain range is
42dB – 50dB in 2dB increments. Note: The TI-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 TI-CMX to lower gain set-
ting 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 meas-
ure 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 consid-
er switching the TI-CMX into a higher gain setting. Another example might be the need
to increase 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 TI-CMX switch-
es to an automatic gain mode (AGC) that optimizes the gain setting automatically in the
hardware of the TI-CMX.
The procedures to adjust the Gain are outlined below:
1. Press the MENU key once to activate the menu items tab.
Press the MENU key multiple times to tab right, and the
ESC key multiple times to tab left, until the TUNE menu is
highlighted and displaying the submenu items.
2. Use the UP and DOWN arrow keys to scroll through the sub
menu items until GAIN is highlighted.
3. Press the LEFT and RIGHT arrow keys to scroll the value.
When the correct Gain is being displayed, press the MEAS
key to return to the measurement screen and begin taking
readings.
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Material sound velocity sound velocity
in/us m/s
Aluminum 0.2510 6375
Beryllium 0.5080 12903
Brass 0.1730 4394
Bronze 0.1390 3531
Cadmium 0.1090 2769
Columbium 0.1940 4928
Copper 0.1830 4648
Glass (plate) 0.2270 5766
Glycerine 0.0760 1930
Gold 0.1280 3251
Inconel 0.2290 5817
Iron 0.2320 5893
Cast Iron 0.1800 (approx) 4572
Lead 0.0850 2159
Magnesium 0.2300 5842
Mercury 0.0570 1448
Molybdenum 0.2460 6248
Monel 0.2110 5359
Nickel 0.2220 5639
Nylon 0.1060 (approx) 2692
Platinum 0.1560 3962
Plexiglas 0.1060 2692
Polystyrene 0.0920 2337
PVC 0.0940 2388
Quartz glass 0.2260 5740
Rubber vulcanized 0.0910 2311
Silver 0.1420 3607
Steel (1020) 0.2320 5893
Steel (4340) 0.2330 5918
Steel Stainless" 0.2230 5664
Teflon 0.0540 1372
Tin 0.1310 3327
Titanium 0.2400 6096
Tungsten 0.2040 5182
Uranium 0.1330 3378
Water 0.0580 1473
Zinc 0.1660 4216
Zirconium 0.1830 4648
Acoustic Velocity Table