Specifications

10. Using the Flaw Alarm / Measurement Gate
Page 68 USN52 L Operating Manual
10.1 Purpose of the Gate
The gate circuit of the USN52 L, displayed as a horizontal bar in
the A-scan, monitors a selected depth range in the material under
test and serves two important functions:
• It activates the built-in alarm when an echo signal in the
gate exceeds (positive logic) or drops below (negative logic)
the user set threshold amplitude.
• It provides time of flight measurements for conversion to
thickness or distance values. Digital measurement values
are displayed in the measurement line and, optionally, in
the enlarged value display area.
10.2 Setting Gate Logic
Use the GATE LOGIC function, in lower level Menu 8, to enable
the gate and select the logic for triggering the alarm. There are 4
possible GATE LOGIC settings:
POSITIVE - Gate is enabled and gate bar displayed in the A-scan
to show its starting point and width. Alarm activates when an echo
exceeds threshold in the gate.
NEGATIVE - Gate is enabled and gate bar displayed in the A-
scan to show its starting point and width. Alarm activates when
no
echo exceeds threshold in the gate.
MEASURE - This setting is for thickness or distance measure-
ment only.
The visual alarm LEDs are disabled; they will not illumi-
nate. Gate is enabled and gate bar displayed in the A-scan to
show its starting point and width. Gate logic is automatically set to
positive.
OFF - Gate is disabled and no gate bar displayed.
NOTE: Digital measurement can be performed with either
positive or negative gate logic.
Set GATE LOGIC or disable the gate as follows:
1. Switch to the lower menu level:
or
2. Select Menu 8, if necessary (GATE LOGIC function is at the
bottom of the middle column):
or
3. Frame the middle column of functions: or
4. Select the desired GATE LOGIC setting:
10. Using the Flaw Alarm / Measurement Gate