Questions & Answers - Thickness Gauging Level 1

by Rolf Diederichs *
Acknowledgement: Before we made this Q&A we read the articles from: Focus on Thickness Measurement in UTonline 10/97
So you may do this also before you start or after you have failed :-)

Click on the results button when you're done

1	Which of the following has the greatest effect on measurement accuracy?
	a) Sound velocity
	b) Probe frequency
	c) Material attenuation
	d) Couplant
2	How do gauges determine thickness?
	a) Echo amplitude
	b) Echo time of flight
	c) Echo frequency
3	What accuracy is the maximum achievable by ultrasonic thickness gauging of steel?
	a) 0,01 inch ~ 0,1 mm
	b) 0,001 inch ~ 0,01 mm
	c) 0,0001 inch ~ 0,001 mm
4	What probe frequency should be used to measure 1 mm steel (0.04 inch) ?
	a) not less than 2 MHz
	b) not less than 10 MHz
	c) not less than 20 MHz
5	What probe frequency should be used to measure plastics of 100 mm (4 inch)?
	a) not more than 0,1 MHz
	b) not more than 1 MHz
6	For thickness gauging the probes must provide a
	a) High amplitude
	b) High frequency
	c) High damping
7	Is it necessary or recommended to see an A-scan during the movement of the probe?
	a) Yes - always
	b) Only for corroded parts
	c) Only for extremely thick parts
	d) Only for extremely thin parts
8	What signal waveform is used for thickness gauging?
	a) rectified signal
	b) not rectified (RF both half waves)
	c) only one-half wave
9	The pulse repetition frequency (PRF) is an important value of thickness gauges
	a) only for scanning
	b) only for high speed on-line measurement
	c) not important
10	Can the use of long cables between probe and gauge produce a significant reading error ?
	a) No
	b) Yes - the zero offset changed
	c) Yes - because of change of echo waveforms

Rolf Diederichs 1. Oct 1997, info@ndt.net.de