Measuring with the Gauge
41
¾ If there is up to three fixed bars plus one flashing bar, but never any reading - this means
the Gauge is receiving unrelated echoes from more than one reflector :
Ö on heavily corroded areas this is often a problem :
try check measurements on an adjacent area of the same material
Ö check the Gauge and Probe together on a test block :
if there is still no reading the Gauge may require servicing
If readings obtained are erratic or unstable
¾ Check that the Probe-assembly is properly connected to both Probe and Gauge, and that
the O-Rings are properly seated in their correct positions
Ö False readings can occur if the Probe-assembly has not been fully screwed onto the
Gauge-body
See : Fitting the Probe-module
, page 18
¾ Check that the Probe and its membrane are correctly assembled with sufficient couplant
Ö Air bubbles inside the membrane can cause false readings
Ö Membrane stretched too tightly over the Probe-face can cause false readings
¾ Ensure that the Probe-frequency is suitable for the probable minimum thickness of the
material being measured
Ö Probe-frequency too low causes doubling and tripling of the actual thickness
See Probe Usage
, page 39
Common reasons which cause difficulty getting readings
¾ Is the Probe-membrane fitted correctly ?
See : Probe/Knurled Ring Assembly
, page 20
Ö Check that there is a thin layer of oil between the membrane and Probe-face, and
with no air-bubbles trapped
Ö Check that the membrane has not been stretched too tightly over the Probe-face
¾ Is the Probe-cable OK ?
Ö Check that the cable is in good condition
Ö Check that the Probe-assembly is correctly fitted onto the Gauge-body
¾ Is the material measurable at all ?
Ö Are the front and back faces of the material parallel ?
Ö Is the material not too corroded ?
Ö Is the material not too thin for the Probe being used ?
It is often worth confirming that the Gauge is operating OK using a test sample – and
also to confirm that the material can actually be measured by ultrasonic multiple-echo
thickness measurement.
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