TL;DR
Sensitivity drift means calibration blocks are showing amplitude changes that were not present before. Perform a full calibration with a certified reference block and check probe connector condition before conducting any aerospace inspections.
What you might see
- calibration block peak amplitude shifted from the stored reference
- indications missed on a reference standard that were found previously
- probe sensitivity varies between scans on the same part
- probe connector shows intermittent signal
Likely causes
Probe wear, element damage, or delaminated active elements reducing sensitivity
Probe connector contaminated with couplant or corrosion increasing contact resistance
Instrument gain drift requiring recalibration per the calibration schedule
Couplant viscosity or application inconsistency affecting acoustic coupling
Required tools
- Certified calibration reference block (applicable to the inspection code)
- Probe element diagnostic function (instrument built-in)
- Cotton swabs for connector cleaning
- Spare probe cable
Safety first
- NDT equipment used on aerospace structural parts must be calibrated per the applicable inspection procedure before each use. Do not conduct inspections with an out-of-calibration instrument.
- Couplant contamination on flight hardware requires containment. Use only approved couplants and remove all residue per the procedure.
Procedure
- 1
Perform a full sensitivity calibration on the certified reference block per the applicable inspection procedure before each use session.[1]
- 2
Compare the current peak amplitude on the reference reflector to the stored calibration value. A deviation above plus or minus 2 dB requires investigation.[1]
- 3
Inspect the probe connector for couplant residue, corrosion, or bent pins. Clean the connector with a dry cotton swab.
- 4
Perform a probe element check using the instrument's built-in element diagnostic function if available. Note any dead or weak elements.
- 5
Swap the probe cable and retest the calibration reflector. If sensitivity recovers, the cable was the cause.
- 6
If sensitivity is still drifted after cable swap, substitute a known-good probe and retest. A confirmed probe fault requires removing the probe from service and sending it for evaluation.
- 7
Document the calibration check and any out-of-tolerance conditions in the inspection log before conducting any inspections.
Sources
GE Waygate Technologies Waygate Phasor XS / DXR NDT Equipment (UT / X-ray / CT) general technical documentation, GE Waygate Technologies
GE Waygate Phasor XS / DXR operator documentation, calibration and probe maintenance procedures (general)
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