Nasaco EML-2 User manual

ELECTRO-
MAGNETIC
LOG
DESIGNED AND
MANUFACTURED
IN ENGLAND
RoHS
2002/95/EC
EML-2

TARGET EM DISPLAY DRILL TEMPLATE

INTRODUCTION.
The EML-2 log consists of a through hull sensor and an interface box which, when
correctly installed, outputs boat speed through the water, trip distance and total
distance. The unit is factory set but has the facility for final in situ calibration.
The output, which updates twice a second, is in the NMEA-0183 format using the
sentences VHW and VLW. The trip distance is reset to zero each time the power is
turned off while the total distance is cumulative and cannot be reset. The EML-2 can
be used with the NASA Marine Clipper or Target EM log display or any other
compatible display.
The EML-2 log is designed for use in GRP hulls.
HOW IT WORKS.
The EML-2 generates an alternating magnetic field in the water below the sensor. As
the sensor passes through the water it generates an alternating electric field whose
amplitude is proportional to the boat's speed through the water. This field is detected
by small stainless electrodes on the underside of the sensor. The interface box then
amplifies this signal and converts it into speed and distance readings. An LED on the
interface box flashes each time new NMEA data is sent out.
CHOICE OF SENSOR LOCATION.
The sensor must remain in non-turbulent water flow at all times. Choose a position as
close to the centre line as possible where the water flow is unrestricted and where the
sensor is accessible for cleaning. Avoid areas around devices which could cause
electrical or magnetic interference.
Ideally the sensor should be: -
- close to the boat's centre line.
- as vertical as possible.
- clear of the keel.
- clear of sources of electromagnetic interference.
- always immersed, no matter what the heel.
- internally accessible for cleaning.
Page 1

INSTALLING THE SENSOR.
IMPORTANT: Read and fully understand the installation instructions and only
proceed if you possess the required skills and correct tools.
WARNING: Always wear safety glasses and a dust mask when installing to avoid
personal injury.
WARNING: Immediately check for leaks when the boat is put back in the water.
WARNING: The O-rings must be intact and, the lower one, properly lubricated to
make a watertight seal.
CAUTION: Never use solvents or products that contain solvents which could attack
the plastic.
IMPORTANT: The sensor in manufactured from glass filled nylon and is designed
for use on the outer skin of a fibre glass hull. Never install the sensor in a wooden hull,
since swelling of the wood could fracture the plastic.
Once a suitable location has been selected, with the boat out of the water, drill a 3mm
pilot hole from inside the hull. Using a 51mm (2.0 inch) hole saw, cut a hole
perpendicular to the hull from the outside of the boat. Using a file, make a small
chamfer around the hole sufficient to accommodate the 2mm radius on the skin fitting
flange. Now sand and clean the hole, inside and outside, to ensure the sealant will
properly bond to the hull.
IMPORTANT: Ensure the hull is of constant thickness under the skin fitting flange so
the nut will fit squarely against the hull.
Using a proprietary brand of marine silicone sealant, apply about 2mm of sealant
around the skin fitting flange where it contacts the hull and also up the sidewall to a
distance 3mm higher than the combined thickness of the hull, the spacer washer and
nut. This will ensure there is sealant in the threads to seal the hull and to hold the nut
securely in place. From the outside of the hull, push the housing into the mounting
hole using a twisting motion to squeeze out excess sealant. With someone outside
holding the skin fitting in position, from the inside apply a 2mm thick layer of sealant
around the hole equal to the diameter of the rubber washer. Then place the rubber
washer over the skin fitting and bed down onto the sealant. Coat the upper face of the
rubber washer with sealant and tighten down the nut taking care not to over tighten it.
(see fig1)
Page 2

Carefully remove all surplus sealant from the inside and outside of the hull and leave
until the sealant has cured. It is recommended that the area around the skin fitting is
thoroughly cleaned and the whole assembly be fibre glassed into the hull as shown in
fig 2. ensuring that the top 20mm of thread remains free of resin or sealant.
Page 3
20mm
Minimum
GRP
Fig 2
Fig 1