The meter we use is the “Tramex Skipper Plus” model which is widely used throughout New Zealand and World Wide by marine surveyors. Unlike moisture meters used in the construction industry, this meter does not use any penetrating probes, therefore not damaging the substrate of the vessel.
Moisture meters are used to detect large amounts of moisture. In a timber vessel this could mean the onset of rot, or in a GRP vessel this could mean osmosis. However the operator must be well versed in the meters use, as their accuracy can measure internal tanks!
Technically, the Tramex Moisture Meter operates on the principle that the electrical impedance of a material varies with it’s moisture content. To measure and detect moisture, the two co-planar conductive rubber electrodes mounted on the base of the instrument case are pressed onto the wood or GRP sample. The instrument measures the electrical impedance of the material being tested by creating a low frequency alternating electric field between the electrodes.
This field will penetrate the material up to a depth of 30mm, depending on the material and range being used. The very small current flowing through the field is inversely proportional to the impedance of the material. The instrument detects this current, determines its amplitude and, after processing, drives the pointer of the moving coil meter to the computed moisture value.
Should you ask for the vessel to be surveyed with a moisture meter?
This is up to the client. A moisture meter is only as good as the surveyor using it. Some surveyors will use a meter regardless, but do remember this adds more time and cost to the survey. At Pacific Rim Marine Surveys Ltd, we always have an instrument with us and will use in the case of concern or request by the client. A good surveyor will carry out the majority of the survey with percussion testing with a small hammer, and visual sight. Normally a moisture meter is used to determine a specific problem that arises.