Questions & Answers - Thickness Gauging Level 3

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1	When using a double crystal probe and changing the type of couplant,
	a) re-calibration is not necessary
	b) Velocity must be re-calibrated
	c) Zero offset must be recalibrated
2	When using the echo amplitude threshold method, in what range is the accuracy error affected by amplitude changes?
	a) 1/2 wavelength
	b) 1/4 wavelength
	c) 1/8 wavelength
3	Can the backing of the object's backwall affect accuracy?
	a) No
	b) Yes - but less than 1/4 wavelength
	c) Yes - but more than 1/4 wavelength
4	What is the most common DSP technique for thickness gauging?
	a) Averaging
	b) Noise suppression
	c) FFT
5	Which method is more accurate?
	a) Zero crossing
	b) Amplitude threshold
6	If the interface is applied to the backwall echo triggering method, how much can the error be affected by the coupling film? (assuming proper handling)
	a) 0,1 mm
	b) 0,01 mm
7	What is the most important factor in performing an accurate thin multilayer measurement ?
	a) Velocity of each layer
	b) Polarity of boundary echo
8	When temperature changes for on-line plastic pipe measurement, is a manual velocity re-calibration always necessary?
	a) Yes
	b) No
9	When measuring the wall thickness of a pipe using the immersion technique and the diameter is very small compared to the probe's diameter, you should use a
	a) Focused probe
	b) Flat probe
10	Can sound attenuation significantly affect the accuracy reading?
	a) No
	b) Yes