Quiz Questions Flashcards
What does HPF stand for?
High Pass Filter
The HPF is used to what?
Eliminate low frequencies which are produced by slow changes (ex. conductivity shift)
What is the main function of the LPF?
Remove high frequency interference noise
Probes for inspection of pipe and tubing are usually of what variety?
Bobbin (ID)
What are drilled holes commonly used to represent?
Pitting
When testing by for surface flaws, how do you want the frequency?
As high as possible
The higher the inductance of a coil at a given frequency…..
The more sensitive the coil will be
What does phase lag have to do with depth?
It increases with discontinuity depth
When is the use of a HPF not recommended?
When scanning manually
When using eddy currents to measure the thickness of a non conductive coating applied to the conductive base, the measurement is based on what?
An impedance due to liftoff
Filters are adjusted in what units?
Hertz
What does the HPF allow?
High frequencies to pass and filters out the low frequencies
What type of probe is most often used to inspect the inside diameter of a machined hole?
Bolt hole probe
Where are sliding probes used to test?
Around the edges of fasteners
What changes the angular relationship on the screen?
Frequency
What does coring a coil do to flux density?
Strengthens it
What happens to the conductivity of a material as the temp of the material increases?
Decreases
What’s another name for hybrid coil?
Reflection coil
Variations from thickness mean you’re using what?
Too high of a frequency
Variations in skin effect effect mean what?
Frequency is too low
Which eddy current machine will detect permeability changes?
ANY machine
When the material temp goes up, what is there more of?
Resistance
When material permeability increases, what happens to the eddy current signals?
They become erratic and distorted
What does the ANGLE of the trace represent?
DEPTH
When will you see eddy currents while using DC?
When the power is being turned on and off
What does it mean if there is no coil in the circuit?
No lag therefor in phase
A coil addition to the circuit means what?
A 90 degree phase lag
Which factor is the lag represented by?
XL
What happens in the XL and the R? (Separately)
R = time/place volt happens XL = time/degree amp happens
The screen on the bridge is where we do what?
Measurements
If the resistance increases, what do you need more of?
Voltage
What do non ferromagnetic materials use as the permeability value in the formula?
ONE
Lower conductivity means what for depth of penetration?
Increased DOP
The impedance has to do with what features?
Coil features
Why do we use coils instead of just wire?
Circular currents will produce a longitudinal magnetic field
What material factor makes eddy currents difficult?
Permeability
Is a DC saturation coil apart of the Wheatstone bridge? If not, what is it considered?
No. It’s considered a hybrid arrangement
What gives a permanent paper record of inspection?
Strip chart
A waterfall display is used with what type of probe?
Spinning/rotary probe
Each line on the waterfall display represents what?
360 degrees
What is the ideal signal to noise ratio?
3 to 1
What are the extreme ends of the eddy current frequency range?
100 Hz to 10 MHz
More permeability means more and less of what?
More skin effect, less depth of penetration
What type of defect would a donut probe be looking for?
Radial crack from bore (crack coming out from hole)
What is the only way to see differences on the screen?
With voltage and current changes
What is the phase lag angle at one standard depth of penetration?
57 degrees
What does a vector describe?
Direction and magnitude
Angle = direction and magnitude = length
