Checkline TI-007DLX, Руководство по эксплуатации

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5.0 MAKING MEASUREMENTS
The steps involved in making measurements are detailed in this section. The following
sections outline how to setup and prepare your TI-007DLX for field use. In pulse-echo
mode the probe zero must be performed on the reference disk (battery disk) attached to
the top of the instrument. This compensates for variation in the transducer. In all modes
the sound velocity must be determined. The sound velocity is used to convert the transit
time to a physical length. The sound velocity can be selected from the material chart at
the end of this manual, or for greater precision determined by measuring and calibrating
from a known thickness of the actual material. To enter the velocity from a table, look
up the material on the chart in the appendix of this manual and refer to the section below
on Calibration to a Known Velocity. To determine the velocity of a single sample, refer
to the Material Calibration section on page 17.
When measuring curved materials, it’s more accurate to calibrate from two test points,
one at the minimum limit of the target thickness and one at the maximum limit. In this
case the reference disk is not used, and considered a ‘two-point’ calibration described on
page 19.
5.1 Probe zero
A probe zero is only necessary if a contact style transducer is used in pulse-echo mode,
and the contact option is enabled in the menu. A probe zero should be done prior to
calibrating the instrument, and done on a periodic basis when a temperature gradient is
an issue. If the TI-007DLX is not zeroed correctly, all measurements will be in error by
some fixed value. In order to perform a probe zero, you must be in pulseecho mode.
Setting the zero point of the TI-007DLX is important for the same reason that setting
the zero on a mechanical micrometer is important. It must be done prior to calibration,
and should be done throughout the day to account for any temperature changes in the
probe. If the TI-007DLX is not zeroed correctly, all the measurements taken may be in
error by some fixed value. The zero can only be performed with the measurement mode
set to pulse-echo (P-E). Therefore, if the TI-007DLX is to use the echo-echo (E-E)
measurement mode and a manual zero is being performed, the TI-007DLX will argue by
briefly displaying the message “ERR”.
The procedure to zero the transducer is outlined as below:
Performing a Manual Probe Zero (On Block)
1. Apply a drop of couplant on the transducer and place the transducer in
steady contact with the disk (battery cover) located at the top of the unit to obtain a
measurement.
2. Be sure all six repeatability/stability bars in the top left corner of the display are
fully illuminated and stable, and last digit of the measurement is toggling
only +/- .001” (.01mm).