Controls on a Digital Display (2) Flashcards
Radio frequency (RF) Display
Baseline is in the middle and signal appear above and below the line.
Rectified or Video Display
- Positive
- Negative
- Full-wave
Positive Rectification
Only the positive part of the wave is shown
Negative Rectification
Both the positive and negative part of the wave are combined to show a single wave
Grids
Help to measure relative height and position of indications
- per cent full screen width (FSW)
- per cent full screen height (FSH)
Pulse Length or Width Control
Determines how long the electric charge hits the crystal or time duration of pulse
- longer pulse = better sensitivity, more penetration, less resolution
Pulse Energy Control
Amount of voltage applied to the crystal
- more voltage = greater sound deformation = more energy sent and more penetration
- longer the ring poorer the resolution
Delay Control
To eliminate the sound travel that is not under inspection (couplant, water, shoe)
Range Control
Expand or contract the horizontal baseline to show more or less material on screen.
- only changes distance between pips not their relative distance to each other
Gain Control
Adjust the amount of returned signals
- won’t affect how loud the transducer is only amplify the received signal to make them easier to see on the screen
- measured in decibels (dB), adding 6dB doubles the amplitude of signals
Reject Control
Can remove lower level signals at the bottom of the screen (grass, noise, hash) that can make the screen hard to read.
Pulse Repetition rate (PRR) or Pulse Repetition Frequency
Determines how often a pulse is sent to the signal, determined by the thickness and velocity of sound within a material, don’t want to overlap signals (ghost signal)
Gates
Used to measure signal height and/or sound paths
- only work when a signal crosses/breaks the gate.
