Measurement Modes; Single Echo Mode (Se) (Mode 2) - Cygnus 1 Ex Manual

Steels Any
Steels Non
Steels Non
Steels Non
Cast Non
Iron
The table above shows to be able to measure both coated and un-coated steels
with non to heavy corrosion ideally you will require at least two probes, in almost
all applications this will be a S2C probe and a T5B probe.
When measuring in Multiple Echo mode the coating will be ignored and
just the metal thickness measured.
It is possible to use a Twin Element (T**) probe in Echo-Echo Mode to
ignore thin paint coatings. However, this method does not have the
ability to verify measurements and without observing the A-Scan
display it is possible to get incorrect measurements.

Measurement Modes

Single Echo Mode (SE) (Mode 2)

Single Echo measurement mode is most useful on heavily corroded metals where
Multiple Echo fails. Because it only needs the first return echo to take a
measurement it performs well on virtually all steel conditions.
However single echo mode will not ignore any surface coatings, so if you measure
through a coating it will give an incorrect metal thickness measurement. If the
surface coating is very thin (0.2mm / 0.01") paint you can make an allowance for
this error, but thicker coatings introduce too much error to be practical.
Single echo measurements use a twin element (twin crystal) probe, because there
are two elements angled to a focal point there is a v-path error introduced.
However, this v-path error is mostly corrected by the gauge, and furthermore by
performing a two-point calibration.
Twin element probes require "zeroing" at regular intervals, especially if the
ambient temperature is changing.
Cygnus 1 Ex Operating Manual
Non to 3 mm+
Moderate (0.12"+)
Non to 0.8 mm+
Heavy (0.03"+)
Non to 1.0 mm+
Heavy (0.03"+)
Non to 1.5 mm+
Heavy (0.06"+)
Non to 2.5 mm+
(0.1"+)
Moderate
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S2C Multiple Echo
T7A Single Echo
T5A Single Echo
T5B Single Echo
T2C Single Echo