Checkline TI-MINIMAX - Manual (Page 137)

MINI-MAX Ultrasonic Bolt Tension Monitor
SURFACE NOISE PROBLEM
NO GATE W/GATE
The diagrams above can be illustrate a typical example of both cases. Let’s start
with the noise condition first. Refer to the
NO GATE diagram: (A) refers to the
noise in front of the true reflection signal (C). Notice that without a gate
activated, the MINI-MAX is detecting on the noise (A) as shown at point (B).
However, the true measurement should be taken at point
(C). Given the
threshold and gain levels the MINI-MAX is currently set to in the NO GATE
diagram, the amplitude from the noise is sufficient enough to cause the MINI-
MAX to detect, or measure the noise rather than the end of the bolt (C).
Now refer to the W/GATE diagram. The horizontal line at the top of (D), is
GATE. The start point of GATE has been adjusted to just beyond the noise (A)
so that the MINI-MAX ignores the noise and detects the true back wall (C). Note:
the MINI-MAX will only detect on signals that are located inside the dimensions
of the
GATE (B). Therefore, the MINI-MAX cannot see (A) at all, with respect to
the starting point of the gate at (B). Also notice, the THR (threshold) level is the
height of the distance (D) from the baseline. Zero threshold is indicated by the
bottom of the range (D), and THR: 6 (threshold) is indicated at the top of the
range at (D). Therefore, the vertical height of GATE1 is the THR (threshold)
level. The threshold level can be increased to decrease sensitivity, or decreased
to increase sensitivity.