Checkline TI-25PX, Руководство по эксплуатации

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3.5 Temperature
Temperature has an effect on sound velocity. The higher the temperature, the slower
sound travels in a material. High temperatures can also damage transducers and present
a problem for various liquid couplants.
Since the sound velocity varies with temperature it is important to calibrate at the same
temperature as the material being measured.
Normal temperature range
Most standard transducers will operate from 0°F to 250°F.
High temperature measurements
Special transducers and couplants are available for temperatures above 250°F up to
1000°F with intermittent contact. It is necessary to cool the transducer by submerging it
in water between measurements.
Modes and temperature errors
In addition to errors caused by velocity changing with temperature, some modes
(measurement techniques) are affected more than others. For example, dual element
pulse-echo mode has larger errors due to changes in the temperature of the transducer.
However, multi-echo techniques offer temperature compensation help to minimize these
errors.
3.6 Measurement Modes
This section will cover the different measurements modes of the TI-25PX, the
transducers required, and the reasons for using specific modes:
Pulse-Echo (P-E) Mode:
Pulse-echo mode measures from the initial pulse (sometimes referred to as an artificial
zero) to the first echo (reflection). In this mode, either an automatic or manual zero
can be performed depending on the zero probe setting. If the manual mode has been
selected, the transducer is placed on the reference disk located on top of the TI-25PX,
and the PRB 0 key pressed to establish a zero point for the transducer connected. If the
Auto Zero feature is enabled, simply pressing the PRB 0 key will perform an electronic
zero to establish the same zero point.
In pulse-echo mode, errors can result from surface coatings and temperature variations.
Since pulse-echo only requires one reflection, it is the most sensitive mode for
measuring flaw/defects when measuring heavily corroded metals.