Prerequisites
The ST90 system is turned on and operates normally.
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The ST90 system is in Normal mode, but TX Power is set to Off to prevent transmissions. |
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The transducer is retracted to its upper position. |
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If the ST90 system is operated from any other compartment than the bridge, an open two-way oral communication channel with the bridge
is required. |
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Neither tools nor instruments are required. You may however find this equipment useful:
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In order to do this test, the ship must be "silent".
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The water must be as deep as possible. Recommended minimum depth is 100 metres. |
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There must be no other vessels in the vicinity. |
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The vessel must lie still in the water. |
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As much machinery as possible must be turned off. It is particularly important to turn off electrical motors, as well as cooling systems and hydraulic pumps that may cause
electric noise. |
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To prevent interference, all other hydroacoustic instruments must be turned off. |
NoteWith the vessel in port, the environmental conditions are not satisfactory. In the shallow waters of the port, noise from other vessels, dockyard workers or machinery will cause unreliable test results. If you do this tests in a busy harbour, or with noise sources present, the sensitive receivers will detect all the noise in
the nearby waters.
Context
To measure the noise, observe the noise values provided on the Noise page in the Diagnostics dialog box.
TipIf you record all the raw data during the noise test, you can repeat the test later using the replay file.
You may wish to make the noise/speed curve under realistic conditions. This means that all relevant vessels systems are in normal use. If you experience very high noise levels, you may wish to repeat the test with "silent ship" settings.
NoteWhen the transducer is fully lowered, the speed of the vessel must not exceed the maximum speed permitted for the hull unit. This maximum speed depends on the physical size of the transducer, the mechanical construction of the hull unit, and how far
down the transducer has been lowered. The System Protection page allows you to define a limit that triggers an alarm if the maximum speed is exceeded. The System Protection page is located in the Installation dialog box.
Illustration:
Read the noise value from the noise circle. Use the mean value of the readouts at 0 degrees (straight up).