IMPACT SUBSEA
INNOVATIVE UNDERWATER PRODUCTS
www.impactsubsea.com
Document No:
0000.1913 |
Version No:
1.2 | 23
rd
April 2020
16
6.1 Understanding FMD Readings
Within the reading window, there is a bar of yellow and green for any measurement that
detects the presence of water/liquid:
The yellow bar shows the total energy level received back at the ISA500 probe.
The green bar shows the proportion of that energy that is a valid echo.
The yellow energy bar ranges from 0 to 1 where 1 represents full saturation of the ISA500 Probe
receiver. An energy level of 0.707 (square root of 2) is the theoretical perfect level as it
represents the energy of a pure sine wave with an amplitude utilising the maximum dynamic
range of the ISA500.
The green bar ranges from 0 to 1 which represents a quality factor of the
returned echo. A
value of 1 would represent a return echo of perfection with negligible noise and distortion.
The correlation value can be used alone as a trust factor where low values would
mean there a
good possibility it's a false reading. A more detailed picture can be built by combining this
information with the energy level as shown in the table:
Low energy levels
High energy levels
Low correlation
Weak signal probably false
reading
High noise level most
likely a false reading
High correlation
Weak signal but likely a good
reading
Ideal conditions very
trust worthy readings
These values can also give some insight for adjusting the transmit power. If the energy level is
low then consider increasing the amplitude of the transmit pulse (under
'Setup'
in the seaView
FMD application).
Please note, it is the responsibility of the user of the ISFMD system to satisfy him/herself as to
the validity of readings.
