DMTA-10004-01EN, Rev. D, November 2016
Using Special Functions
119
STANDARD
The standard alarm warns you when the actual measured thickness is below a
low reference value or above a high reference value. The reference values are
thickness set points using the current instrument units and resolution.
PREVIOUS THK
To use this function, you must first open a previously stored inspection file. The
alarm uses the previous thickness value as its reference when determining if the
actual thickness is in a high or low alarm condition. The previous thickness alarm
warns you when the actual measured thickness is outside the alarm reference
values when compared to the previous thickness value at each ID location within
the file.
You can choose the ABSOLUTE DIFF (differential) mode to set the following
parameters:
— When the thickness differential is smaller than or equal to the ABSOLUTE
LOSS value, a low alarm is indicated.
— When the thickness differential is greater than the ABSOLUTE GROWTH
value, a high alarm is indicated.
Table 8 on page 119 shows the result for an example where both ABSOLUTE
LOSS and ABSOLUTE GROWTH are set to 1.27 mm (0.05 in.).
You can also choose the %DIFF (differential) mode to set the following
parameters:
— When the thickness differential is smaller than or equal to the %LOSS value,
a low alarm is indicated.
Table 8 Alarm calculation example with the ABSOLUTE DIFF mode
Previous
values
Actual
thickness
Low alarm High alarm Calculations
7.62 mm
(0.300 in.)
6.07 mm
(0.239 in.)
Yes No 7.62–6.07 > 1.27 mm
(0.300–0.239 > 0.050 in.)
7.62 mm
(0.300 in.)
8.03 mm
(0.316 in.)
No Yes 8.03–7.62 > 0.127 mm
(0.316–0.300 > 0.005 in.)
7.62 mm
(0.300 in.)
7.24 mm
(0.285 in.)
No No 7.62 – 7.24 < 0.127 mm
(0.300–0.285 < 0.050 in.)
7.62 mm
(0.300 in.)
7.67 mm
(0.302 in.)
No No 7.67 – 7.62 < 0.127 mm
(0.302–0.300 < 0.005 in.)
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