Quiz Questions

Question 1

What does HPF stand for?

Answer 1

High Pass Filter

Question 2

The HPF is used to what?

Answer 2

Eliminate low frequencies which are produced by slow changes (ex. conductivity shift)

Question 3

What is the main function of the LPF?

Answer 3

Remove high frequency interference noise

Question 4

Probes for inspection of pipe and tubing are usually of what variety?

Answer 4

Bobbin (ID)

Question 5

What are drilled holes commonly used to represent?

Answer 5

Pitting

Question 6

When testing by for surface flaws, how do you want the frequency?

Answer 6

As high as possible

Question 7

The higher the inductance of a coil at a given frequency…..

Answer 7

The more sensitive the coil will be

Question 8

What does phase lag have to do with depth?

Answer 8

It increases with discontinuity depth

Question 9

When is the use of a HPF not recommended?

Answer 9

When scanning manually

Question 10

When using eddy currents to measure the thickness of a non conductive coating applied to the conductive base, the measurement is based on what?

Answer 10

An impedance due to liftoff

Question 11

Filters are adjusted in what units?

Answer 11

Hertz

Question 12

What does the HPF allow?

Answer 12

High frequencies to pass and filters out the low frequencies

Question 13

What type of probe is most often used to inspect the inside diameter of a machined hole?

Answer 13

Bolt hole probe

Question 14

Where are sliding probes used to test?

Answer 14

Around the edges of fasteners

Question 15

What changes the angular relationship on the screen?

Answer 15

Frequency

Question 16

What does coring a coil do to flux density?

Answer 16

Strengthens it

Question 17

What happens to the conductivity of a material as the temp of the material increases?

Answer 17

Decreases

Question 18

What’s another name for hybrid coil?

Answer 18

Reflection coil

Question 19

Variations from thickness mean you’re using what?

Answer 19

Too high of a frequency

Question 20

Variations in skin effect effect mean what?

Answer 20

Frequency is too low

Question 21

Which eddy current machine will detect permeability changes?

Answer 21

ANY machine

Question 22

When the material temp goes up, what is there more of?

Answer 22

Resistance

Question 23

When material permeability increases, what happens to the eddy current signals?

Answer 23

They become erratic and distorted

Question 24

What does the ANGLE of the trace represent?

Answer 24

DEPTH

Question 25

When will you see eddy currents while using DC?

Answer 25

When the power is being turned on and off

Question 26

What does it mean if there is no coil in the circuit?

Answer 26

No lag therefor in phase

Question 27

A coil addition to the circuit means what?

Answer 27

A 90 degree phase lag

Question 28

Which factor is the lag represented by?

Answer 28

XL

Question 29

What happens in the XL and the R? (Separately)

Answer 29

``` R = time/place volt happens XL = time/degree amp happens ```

Question 30

The screen on the bridge is where we do what?

Answer 30

Measurements

Question 31

If the resistance increases, what do you need more of?

Answer 31

Voltage

Question 32

What do non ferromagnetic materials use as the permeability value in the formula?

Answer 32

ONE

Question 33

Lower conductivity means what for depth of penetration?

Answer 33

Increased DOP

Question 34

The impedance has to do with what features?

Answer 34

Coil features

Question 35

Why do we use coils instead of just wire?

Answer 35

Circular currents will produce a longitudinal magnetic field

Question 36

What material factor makes eddy currents difficult?

Answer 36

Permeability

Question 37

Is a DC saturation coil apart of the Wheatstone bridge? If not, what is it considered?

Answer 37

No. It’s considered a hybrid arrangement

Question 38

What gives a permanent paper record of inspection?

Answer 38

Strip chart

Question 39

A waterfall display is used with what type of probe?

Answer 39

Spinning/rotary probe

Question 40

Each line on the waterfall display represents what?

Answer 40

360 degrees

Question 41

What is the ideal signal to noise ratio?

Answer 41

3 to 1

Question 42

What are the extreme ends of the eddy current frequency range?

Answer 42

100 Hz to 10 MHz

Question 43

More permeability means more and less of what?

Answer 43

More skin effect, less depth of penetration

Question 44

What type of defect would a donut probe be looking for?

Answer 44

Radial crack from bore (crack coming out from hole)

Question 45

What is the only way to see differences on the screen?

Answer 45

With voltage and current changes

Question 46

What is the phase lag angle at one standard depth of penetration?

Answer 46

57 degrees

Question 47

What does a vector describe?

Answer 47

Direction and magnitude Angle = direction and magnitude = length