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5 Operation CNDAC
204 Rev. 9 (09/2023) Krautkrämer USM 100
5.26 CNDAC
CNDAC (China Distance Amplitude Correction) is an
evaluation method for ultrasonic weld testing, based on
the standards JB/T4730 and GB 11345 of the People's
Republic of China.
In CNDAC, reference lines are defined for:
● the rejection (Reject Line RL),
● the amplitude measurement (Sizing Line SL), and
● the evaluation (Evaluation Line EL).
Defined as references are side-drilled holes having cer-
tain diameters.
The option Custom in the function Code allows the
specification of an own reference block, whose data
must be documented separately.
Evaluations according to CNDAC
After recording the reference echo, the CNDAC shows
the reference lines
RL , SL , and EL depending on the
corresponding choice in the functions Code (standard)
and Cal Block (reference block).
The reference line SL is used for the amplitude mea-
surement. It can be assigned to all gates available
(reading =
SLA , SLB , optionally SLC ).
Examples:
SLA indicates the difference in amplitude of an echo in
the gate A in relation to the reference curve SL at the
position of the echo in dB.
dBrA is identical with SLA .
A%rA indicates the difference in amplitude of an echo
in the gate A in relation to the reference curve SL at the
position of the echo in %. In this connection, the refer-
ence curve at the position of the echo is assumed at
100 %.