Airmar ST900 Owner's Manual & Installation Instructions

OWNER'S GUIDE & INSTALLATION INSTRUCTIONS
Thru-Hull, Retractable with Valve
Ultrasonic Speed & Temperature
Models: ST900, ST950
U.S. Patent 6,426,918; 6,671,225; 6,678,208. EP 1 634 087
Follow the precautions below for optimal
product performance and to reduce the risk of
property damage, personal injury, and/or death.
WARNING: Always wear safety glasses, a dust mask,
and ear protection when installing.
WARNING: The valve is not a watertight seal!
Always install the ultrasonic insert or the blanking plug
secured with the (ST950 insert nut) cap nut and safety
wire for a watertight seal.
WARNING: ST950—The ultrasonic insert or the
blanking plug must be installed in a housing with a
valve. When the valve assembly is removed, always
install the short emergency plug secured with the cap
nut and safety wire for a watertight seal.
WARNING: The o-rings must be intact and well
lubricated to make a watertight seal.
WARNING: Always attach the safety wire to prevent the
ultrasonic insert or blanking plug from backing out in the
unlikely event that the cap nut fails or is screwed on
incorrectly.
WARNING: Immediately check for leaks when the
boat is placed in the water. Do not leave the boat
unchecked for more than three hours. Even a small
leak may allow considerable water to accumulate.
CAUTION: Never pull, carry, or hold the sensor by its
cable; this may sever internal connections.
CAUTION: Plastic housing—Never use a fairing with
a plastic housing. The protruding sensor would be
vulnerable to damage from impact.
CAUTION: Bronze housing—Never install a metal
housing on a vessel with a positive ground system.
CAUTION: The arrow on the top of the ultrasonic
insert must point forward toward the bow to align with
the water flow.
CAUTION: The bottom of the ultrasonic insert must be
flush with the bottom of the housing.
CAUTION: The sensor must be in good contact with
the water at all times.
CAUTION: Never use solvents. Cleaner, fuel, sealant,
paint, and other products may contain solvents that can
damage plastic parts, especially the sensor's active face.
IMPORTANT: Read the instructions completely
before proceeding with the installation. These
instructions supersede any other instructions in your
instrument manual if they differ.
Record the information found on the cable tag for future reference.
Part No.________________Date___________Frequency_________kHz
ST900
B120, P120
housing
Applications
• Not recommended for boats designed to pull air under the hull.
• Plastic housing recommended for fiberglass or metal hull only.
Never install a plastic housing in a wood hull since swelling of
the wood may fracture the plastic.
• Bronze housing recommended for fiberglass or wood hull only.
Never install a bronze housing in a metal hull because
electrolytic corrosion will occur.
• ST900 with plastic housing recommended for an aluminum hull
less than 6mm (1/4") thick.
How the Ultrasonic Speed Sensor Works
The speed sensor uses ultrasonic pulses to collect echoes from
small particles in the water as they pass under two transducers
embedded in the insert (see Figure 1). These transducers monitor
the particles in their respective beams. As the boat travels through
the water, both transducers 'view' the same stream of particles.
Because it takes time for particles to travel between the two
transducers, the aft transducer detects the particles later than
does the fore transducer. By measuring this time lapse, the
instrument calculates the boat speed. If the boat is airborne, even
for a short time, or in highly aerated water, the sensor will
measure an incorrect speed.
scanning transducer
Figure 1. Monitoring particles in the water
Copyright © 2002 Airmar Technology Corp.
ST950
B17, P17
housing
hull
AFT FORE
vessel direction
particle stream