1 What has the main effect on measurement accuracy Sound velocity
Probe frequency
Material attenuation
Couplant
4 How gauges determine the thickness - by Echo amplitute
Echo time of flight
Echo frequency
7 What accuary is maximum achievable by ultrasonic thickness gauging of steel 0,01 inch ~ 0,1 mm
0,001 inch ~ 0,01 mm
0,0001 inch ~ 0,001 mm
8 What probe frequency should be used to measure 1 mm steel (0.04 inch) not less than 2 MHz
not less than 10 MHz
not less than 20 MHz
9 What probe frequency should be used to measure plastics of 100 mm (4 inch) not more than 0,1 MHz
not more than 1 MHz
11 For thickness gauging the probes must provide a High amplitude
High frequency
High damping
14 Is it neccesary or recommended to see an A-scan during moving the probe Yes - always
Only for corruded parts
Only for extrem thick parts
Only for extrem thin parts
17 What signal waveform is used for thickness gauging recified signal
not rectified (RF both half waves)
only one-half wave
23 The pulse repetition frequency (PRF) is an importand value of thickness gauges only for scanning
only for high speed on-line measurement
not importand
27 Can the use of long cables between probe and gauge produce an significant reading error No
Yes - the zero offset changed
Yes - because of change of echo waveforms
28 What can be the velocity set-up error for type of material, such as "steel" or "stainless steel". 0,5%
2,0%
10,0%
15 Why double cristal probes are used for thickness gauging Good for corrosion gauging
Good for thin wall gauging
Good for thick wall gauging
Good for precision gauging
29 Temperature affects the indicated reading through four mechanisms, what course the main error of these Speed of sound
True thickness of material
Electronics drift
Probe characteristics
5 What is the in-comon clock frequency of precision thickness gauges 1 MHz
10 MHz
200 MHz
13 What can prefent the error which occures by the change of echo amplitude DSP Digital Signal Processing
AGC Automatic Gain Control
Zero crossing Method
2 What gives a better accuracy Direct contact with double crystal probe
Direct contact with delay line probe
Immersion
3 What provides the best minimum thickness resolution triggering between excidation pulse and first backwall echoes
triggering between interface echo and first backwall echoes
triggering between two successive backwall echoes
12 Thickness gauging can only be performed by known velocity Yes
No - methods excist that can measure by unknown velocity
22 Manual thickness scanning requires A-scan display
High-Low peak monitor or latch
26 An ultrasonic gauging measures pipe thickness and simultaniously the inner and outer diameter. What are the benefits of that. Accurate
Relative low System costs
All values measured at the same point
20 When using a double crystal probe and changing the type of couplant, Recalibration is not nessecary
Velocity must be recalibrated
Zero offset must be recalibrated
10 When using the echo amplitude threshold method, in what range is the accuary error affected by amplitude changes 1/2 wavelength
1/4 wavelength
1/8 wavelenght
18 Can the backing of the object's backwall effect the accuracy No
Yes - but less than 1/4 wavelength
Yes - but more than 1/4 wavelength
21 What is the most in comon DSP technique for thickness gauging Averaging
Noise suprecion
FFT
6 What method provides the better accuracy Zero crossing
Amplitude threshold
16 Applied is the interface to backwall echo triggering method. How much can be the error effected by the coupling film (precondition a proper handling) 0,1 mm
0,01 mm
19 What is the most importand factor to perform an accurate thin multilayer measurement Velocity of each layer
Polarity of boundary echo
24 When temperature changes for on-line plastic pipe measurement, is always a manually velocity recalibration nessassary. Yes
No
25 When measuring the wall thickness of a pipe in immersion technuiqe and the diameter is very smal against the probe diameter, it should be used a Focused probe
Flat probe
30 Can the sound attenuation affect the reading accuaracy significantly No
Yes