Dakota Ultrasonics MVX - Manual (Page 67)

MVX High Performance Thickness Gauge
7.6 Gates
The MVX is equipped with two gates that can be adjusted by the user to measure a
specific region or area on and between waveforms. In pulse - echo, only a single
gate can be used. The single gate has a threshold and a start point. In echo - echo
mode, two gates are used. The same threshold level is associated with both gates.
The first gate has a starting point and threshold, and the second gate has a start time
that is determined by adding an adjustable HOLD OFF, or delay, to the return echo
measured by the first gate. These features are described in more detail below:
Note: In order to adjust the gates they must be activated. The gates will only be
active if the measurement mode is set to P-E GT (pulse – echo w/gate1), or E-E
(echo – echo w/ gates 1&2). If the gates are not active, they will be grayed out in the
hot and tabbed menus. The explanations that follow assume that the proper
measurement mode has been selected. Refer to page 28 for additional information
on selecting the measurement mode.
Gate 1
GATE 1 is used in both pulse-echo and echo-echo modes. It has a threshold and a
start time. The purpose of GATE 1 is to prevent the MVX from measuring unwanted
surface noise. This is accomplished by changing the start time of GATE 1. It may be
advantageous to activate a gate when measuring aluminum, titanium, and stainless
steel using lower frequency transducers. However, if a high frequency transducer is
being used, the gate may not be necessary. Aluminum sometimes has an inherent
surface noise problem that can cause erroneous readings from the noise just
following the initial pulse. By blocking the surface noise with GATE 1 this error is
eliminated. GATE 1 is also used in echo - echo mode to force the MVX to measure
between the first and second back wall echoes, by moving the start to the first back
wall reflection of the test material.
The procedures to adjust Gate 1 are outlined below: