TM 1-1520-253-23
2.15.3.5
Reference Standard. The reference standard used for calibration has one half of its working surface cad-
mium plated. This provides the user an opportunity to identify conductivity changes related to cadmium plating varia-
tions. The reference standard has been covered with a layer of teflon tape to (1) protect the cadmium plating and (2)
provide a facsimile of the lift off encountered from the main rotor hubs painted surface.
2.15.3.6
NDI Equipment Settings.
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.
Frequency F1-
100 KHz
F2
-off
HdB-
76.0
VdB-
82.0
260_
Rot-
Probe Drive-
Low
LPF-
100
HPF-
0
H Pos-
80%
V Pos-
30%
Refer to Eddy Current Method, paragraph 1.4.11, TM 1-1520-253-23
b. Set up on the reference standard as follows:
(1)
Place a piece of teflon tape across the probe tip. Replace as necessary.
(2)
Null the probe on the test block.
(3)
Adjust phase as required to obtain horizontal lift-off.
(4) Slide the probe over all three notches in test block. Adjust gain to obtain a three block vertical sig-
nal when probe is passed over the 0.040 inch notch. Refer to the standard instrument display shown in Figure 1-7,
TM 1-1520-253-23.
(5) Note the differing conductivity locations of the flying dot with the probe placed on the non-cadmium
plated portion of the reference standard versus the probe located on the cadmium plated portion. Reference Figure
2.15B below.
Figure 2.15B displays the conductivity variation between
cad and non-cad areas on the calibration standard.
Cadmium variations will raise or lower the flying dot along
the dotted line representing the conductivity curve as
conductivity values change.
Figure 2.15B
2-32
Change 2
