Checkline DFX-7 - Manual (Page 52)

Dakota Ultrasonics
48
6.2 Probe zero
The next step is to perform a probe zero. The zero function is a very important and
necessary function that must be done prior to calibration. It should be done on a
regular basis. In fact, the DFX-7 has been programmed to force this issue at regular
intervals during operation if it hasn’t been done. If the DFX-7 is not zeroed correctly,
all the measurements taken may be in error by some fixed value. When the DFX-7 is
using the auto zero (electronic zero), the DFX-7 can be in any measurement mode.
However, when the manual zero is being used, the DFX-7 must be in pulse-echo
mode in order to perform the zero. The DFX-7 will also see to it that this occurs by
simply forcing the gauge into this mode when zero. Therefore, if the DFX-7 is in the
echo-echo measurement mode and a manual zero is being performed, the DFX-7 will
put the gauge into pulse-echo mode automatically before performing the zero. While
this is a very convenient feature of the DFX-7, the user should be sure to check the
measurement mode following calibration to be sure the DFX-7 is in the desired mode.
The following steps outline both of these techniques.
The DFX-7 is equipped with two zero options:
1) Off Block Zero (Automatic Probe Zero) – When this feature is enabled the
DFX-7 will do an electronic zero automatically, eliminating the need for a zero
disk or block.
2) On Block Zero (Manual Probe Zero) – When this feature is enabled the
transducer must be placed on the probe zero disk (battery cover located on the
top of the unit.
Both zero procedures are outlined as follows:
Performing an Auto Probe Zero (Off Block)
Coating Probe Identified Coating Probe Not Identified
1) Be sure all couplant has been removed from the face of the transducer.