Measuring with the Gauge
38
MEASUREMENT
The Cygnus 1 ROV Gauge is designed to provide accurate, reliable readings on most types
of surfaces using the Multiple-echo method described on page 8
Preparing to take Measurements
Ö Ensure that the Probe is correctly fitted with a membrane, and with membrane oil
correctly applied. See Probe / Knurled-Ring Assembly
, page 20
Ö We recommend that the complete Cygnus 1 ROV System should always be connected
together, and test measurements made, before deployment – and if there are any
datalink problems : use the supplied Test-cable to confirm the datalink is OK
Measurement Underwater
Ö When measuring underwater : there is no need to use a couplant - the water itself is a
good couplant
Ö It is not essential for the Probe to be in direct contact with the surface of the material
being measured, but the Probe should be as close as possible for maximum echo-
strength
Ö The Probe must always be facing directly towards the surface of the material – if the
Probe is facing at an angle it will not be possible to obtain a multiple-echo measurement
Measurement in Air
Ö When measuring in air : always use a couplant to enable ultrasound to enter the test
material.
Water, oil or gel are all suitable couplants, depending on application and preference.
Ö Remove all scale, calciferous marine growth, dirt or loose coating and brush or scrape
the test area clean.
Ö Protective coatings such as paint or epoxy resin need not be removed, provided that
their adherence is good.
Ö Place the Probe-face on the clean, lubricated test surface and make firm contact.
Echo-Strength Bargraph
The green bargraph display indicates ultrasonic coupling-strength :
¾ A single flashing bar means there is no contact at all
¾ One or two bars, plus a flashing bar, means there is not enough contact to obtain three
echoes
Ö This indicates either poor contact, or badly corroded material
Ö This can also occur if the Probe membrane has been fitted incorrectly
¾ Three bars, plus one flashing bar, means there is good contact, but a valid triple-echo
measurement has not been obtained
Ö This probably indicates badly corroded material
¾ Four bars, plus one flashing bar, shows an accurate triple-echo measurment
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