Eddy current

Question 1

which component in an eddy current inspection system provides current to the test coil?

Answer 1

oscillator

Question 2

which component converts changes in eddy current magnitude and distribution into signals to be processed?

Answer 2

bridge circuit

Question 3

what effect does high conductivity have on eddy current depth of penetration?

Answer 3

reduced depth of penetration

Question 4

what’s the term for signal changes caused by the eddy current field intercepting a corner of a part?

Answer 4

edge effect

Question 5

if all other factors remain unchanged what effect does higher frequency have on eddy current depth of penetrations?

Answer 5

shallower depth of penetration

Question 6

what’s the definition of the standard depth of penetration of eddy currents?

Answer 6

point where eddy current strength drops to 36.8% of surface strength

Question 7

how many times deeper than the standard depth of penetration is the effective depth of penetration?

Answer 7

3 times

Question 8

what’s the desirable signal-to-noise ratio for flaw detection?

Answer 8

3 to 1

Question 9

how can you eliminate line voltage fluctuations that may be affecting your signal-to-noise ratio?

Answer 9

switch to a battery powered unit

Question 10

based on application, what are the three general classifications of eddy current probes?

Answer 10

1. surface 2. Inside diameter (ID) 3. Encircling

Question 11

what characteristics of a probe determine the surface area inspected?

Answer 11

diameter of the probe and any shielding in the probe

Question 12

what type of eddy current probes concentrate the field directly under the coil and overcome many of the problems associated with edge effect?

Answer 12

shielded probes

Question 13

what’s the definition of impedance?

Answer 13

total opposition to the flow of AC in an eddy current coil

Question 14

Where do phase angles form?

Answer 14

where the sine waves, representing 2 elements of AC, cross

Question 15

What does the line (formed on a CRT) between the dot with the probe off the part (Po) and the dot when the probe is placed on the part (P1) represent?

Answer 15

lift off

Question 16

how can you configure impedance plane instruments to measure amplitude changes only?

Answer 16

calibrate the unit in the sweep display mode

Question 17

how much operating time remains when the low-battery indicator indications appears?

Answer 17

1/2 hour

Question 18

Which control on the Nortec 2000 is used to adjust numerical parameters or the display appearance, depending on the function selected?

Answer 18

smartknob

Question 19

What key is pressed on the Nortec 2000 to display information to adjust the basic operating conditions of the unit, such as frequency or gain?

Answer 19

MAIN/FILTER key

Question 20

Which function key will activate the bolt hole scanner controls?

Answer 20

SETUP/SPECIAL key

Question 21

Which of the two immediate executions keys is used to execute an instrument operation or respond to a prompt?

Answer 21

ENTER key

Question 22

Which menu soft key would you press after the MAIN key in order to change horizontal and vertical gain together?

Answer 22

press gain menu soft key after you’ve pressed the MAIN key

Question 23

What is the operating frequency range of the Nortec 2000?

Answer 23

100 Hz to 12Mhz

Question 24

what two ways can the phase angle or rotation be set?

Answer 24

using the smartknob or INC/DEC keys

Question 25

Which two keys must be pressed before you can adjust the sweep with the smartknob?

Answer 25

first the DISP key then the DISPLAY key

Question 26

From which menu would you start to reset the unit to factory default settings?

Answer 26

SETUP menu

Question 27

Where should the flying dot be located after nulling is complete?

Answer 27

50 percent full screen height and 50% full screen width

Question 28

What must you make sure of when placing the probe on the crack standard?

Answer 28

make sure probe is on a good area away from any cracks

Question 29

When is the sensitivity check required?

Answer 29

when using the Air Force General Purpose reference standard

Question 30

during surface flaw detection, how would you estimate a discontinuity's size?

Answer 30

by comparing it's indication with your crack standard's indication

Question 31

how should you scan a part to avoid missing small cracks?

Answer 31

move the probe perpendicular to the probable direction of defects

Question 32

what materials should not be used to make eddy current fixtures?

Answer 32

conductive materials

Question 33

what happens to an eddy current signal from defects of the same size as one of the defects increases in depth below the surface?

Answer 33

it decreases

Question 34

What is the most important dimension of a crack?

Answer 34

depth

Question 35

What's the most important fact about the AF general Purpose Eddy Current Standard?

Answer 35

it is the only authorized eddy current standard to be used without a specific waiver

Question 36

what are three examples of artificial defects in eddy current standards?

Answer 36

1. EDM 2. Saw 3. Machine notches

Question 37

what is the primary purpose of any standard?

Answer 37

provide you with a uniform response directly related to the condition or material property you are detecting or measuring

Question 38

What two fators must be tightly controlled during manufacture of an eddy current standard?

Answer 38

material specification and fabrication requirements

Question 39

What system is conductivity measurement based on?

Answer 39

International Annealed Copper Standard (IACS)

Question 40

What shim thickness is used when calibrating the Nortec 2000 liftoff for conductivity testing?

Answer 40

0.004 inch

Question 41

What do you isolate when you look for specified amount of conductivity change?

Answer 41

heat damage

Question 42

What temperature difference between the standards and the part will prevent your from performing conductivity testing?

Answer 42

10 degrees F or more

Question 43

What must you do if during conductivity testing you discover the calibration of the instrument is no longer valid?

Answer 43

recheck all readings taken since last calibration once unit is recalibrated