
D – ALTIMETER
DPN 402197 © TSS (International) Ltd Page 3 of 18
D.2.3 Mounting
Position the altimeter away from other acoustic instruments that may cause interfer-
ence, this may be necessary even if the other instrumentation is operating at a differ-
ent frequency due to the “near field” effect of the acoustic transmission.
Make sure the altimeter is positioned away from turbulence such as propeller noise or
anything that could cause aeration in the water, (acoustic signals are greatly attenu-
ated by the interface between sea water and air bubbles).
Figure D–1: Mounting arrangement
Mount the altimeter using part number 305676, as shown in figure D–1, or a secure
mounting bracket with, rubber protective sleeve around the altimeter body, making
sure the altimeter transducer is the nearest point to the seabed, in other words there
must be no metal work that could conduct the acoustic signal to the transducer by-
passing the water column. Remember the minimum range is 0.8 metres therefore if
an under range data output is to be avoided mount the altimeter at least 0.8 metres
above the bottom.
Make sure the altimeter is mounted perpendicular to the horizontal flying position of
the sub sea vehicle, the beam angle is limited to 9º therefore any misalignment has a
detrimental effect on the operation of the altimeter. Ensure the mounting is secure
and not liable to vibration or movement.
Although the specification quotes 9º beam width the coverage area may increase at
minimum range due to the “side lobes” produced by the acoustic transducer. This can
be caused by a strong reflector close to the altimeter being reflected before the main
beam echo is received thus causing the object to be seen before the main beam is
reflected off the seabed. This situation would cause a reduced range to be recorded.
Make sure the anodised aluminium finish is not damaged as this will cause corrosion
when the instrument is next deployed.
Connect an optional safety leash from the altimeter end cap using a stainless steel
8mm bolt and two washers. Make sure the M8 bolt does not protrude to the alumin-
ium bulkhead as this will damage the anodising.
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