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Go Back   SailNet Community > On Board > Gear & Maintenance > Low Cost General Tools Moisture Meter?
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Thread: Low Cost General Tools Moisture Meter? Reply to Thread
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Topic Review (Newest First)
12-11-2012 05:08 PM
Maine Sail
Re: Low Cost General Tools Moisture Meter?

Quote:
Originally Posted by Curly Furler View Post
It's been over a year since the CT33 was last recommended and I was spotted this:
Electrophysics Model GRP200 Fiberglass Moisture Meter for $199.

Does anyone know if this is a better tool than the CT33 for the novice hoping to save on boat survey costs?

Thank you!

Personally I just prefer a needle/analog moisture meter to one with a digital scale. Perhaps just because I am used to it but I like to watch for changes on the needle vs. a digital read out.. The GRP200 also reads deeper, to 1.5", which you'll likely not need for a simply cursory check of a deck...
12-11-2012 04:35 PM
hellosailor
Re: Low Cost General Tools Moisture Meter?

Apprently the CT33 is designed for wood and the GRP for glass-reinforced-plastic but you might want to ask the maker directly if the range they are measuring is the same.
12-11-2012 04:30 PM
Curly Furler
Re: Low Cost General Tools Moisture Meter?

It's been over a year since the CT33 was last recommended and I spotted this:
Electrophysics Model GRP200 Fiberglass Moisture Meter for $199.

Does anyone know if this is a better tool than the CT33 for the novice hoping to save on boat survey costs?

Thank you!
04-24-2011 08:53 AM
JimsCAL
Quote:
Originally Posted by hellosailor View Post
Sorry to wake the dead...but I've seen comments that most of the moisture meters, including the Electrophysics, are actually capacitance meters. Oddly enough I have a capacitance meter, and a multimeter with a capacitance scale. Both read in microFarads, the standard measure of capacitance.

Which leaves me to wonder, does anyone know how the readings from some of these moisture meters actually translate into real capacitance (mF) and would it then be practical to just use the c.meter as a moisture meter, correlating say x mF as "dry, xx as "damp", xxx as soaked ?

Anyone have both types of meter, to make a comparison with?
The DMM is not "pinless" so unless you want to drill holes all over your deck to get to the core, it won't work.
04-23-2011 11:32 PM
TakeFive
Quote:
Originally Posted by hellosailor View Post
Sorry to wake the dead...but I've seen comments that most of the moisture meters, including the Electrophysics, are actually capacitance meters. Oddly enough I have a capacitance meter, and a multimeter with a capacitance scale. Both read in microFarads, the standard measure of capacitance.

Which leaves me to wonder, does anyone know how the readings from some of these moisture meters actually translate into real capacitance (mF) and would it then be practical to just use the c.meter as a moisture meter, correlating say x mF as "dry, xx as "damp", xxx as soaked ?

Anyone have both types of meter, to make a comparison with?
You are correct that all pinless moisture meters actually measure capacitance. So a moisture meter will read high moisture levels where there are backing place, ribs, stringers.

I played around with the cheapo General Tools meter listed above, and with a $50 Ryobi, along with a borrowed CT33. None of them correlate with each other particularly well, and I think the reason is that they all have different "depth perception" based on their sensitivity. The GT meter was totally useless - readings were noisy and irreproducible. The Ryobi could be a useful tool for finding the source of water intrusion via gradients of moisture. But it does not correlate well with the CT33, which is sort of the "gold standard" that all surveyors use.

Electronic stud finders work on the same principle. I've used mine occasionally to track down moisture locations.
04-23-2011 11:21 PM
hellosailor Sorry to wake the dead...but I've seen comments that most of the moisture meters, including the Electrophysics, are actually capacitance meters. Oddly enough I have a capacitance meter, and a multimeter with a capacitance scale. Both read in microFarads, the standard measure of capacitance.

Which leaves me to wonder, does anyone know how the readings from some of these moisture meters actually translate into real capacitance (mF) and would it then be practical to just use the c.meter as a moisture meter, correlating say x mF as "dry, xx as "damp", xxx as soaked ?

Anyone have both types of meter, to make a comparison with?
01-16-2010 07:26 PM
TakeFive I thought I should circle back with an update. The General Tools meter was very disappointing. Horrible reproducibility and readings were so noisy that the audio feedback feature just made a constant clicking noise. I returned it immediately. Mainesail was right about it.
12-29-2009 08:09 AM
boatpoker
more meter complications

I just re-typed the following from The Masthead - Journal of the Westlawn Instition of Marine Technology, December 2009 issue. Although there are a few things I mildly disagree with, it generally supports my position that a great deal of experience is required to use these meters effectively.
Note : The "CoreMat" referred to is a very commonly used glass fabric that looks like a very thick paper towel.

Know it All Contest Solution to the September 2009 Question
Wet Moisture Readings
By Dave Gerr, © 2009 Dave Gerr

The Know It All questions and correct answers are important design tips for students as well as other marine professionals. We suggest that you file them away for future reference.

The question from the September issue was :
It's early spring on a cool clear day. The weather has been dry for a couple of weeksand you are surveying Dancing Daisy, a 1992, 38 foot,cruising sailboat with a moderate fin keel. The hull, deck and cabinare all cored fiberglass except for the solid glass region at the centerline (in the keel and stem area). Dancing Daisy has been hauled out all winter and is well ventilated under an open shed.

You have taken moisture meter readings high on Dancing Daisy's topsides as a baseline and find that - in comparison - most of the deck and cabin top, as well as the hullbottom are reading wet (though not the cabin sides). There are no signs of water penetrationproblems. Are the meter readings an indication that these regions are suffering from water saturation or is there some other explanation ? If so, what is it ?

The correct Answer Is :

The answer is no. Though a number of "no" answers were submitted, the explanations were based on the presence of condensation which is not the likely cause. In fact condenstation on the hull surface shouldn't through readings too far off. The most likely explanation for the apparent wet readings is that the builderhas used a layer of CoreMat on the topsides and on the cabin sides where the smoothest possible surface with no print-thru was desired. (There are better ways to achieve this end but using CoreMat as a print blocker is common and acceptable.) CoreMat wasn't used on the deck or cabin top where print through is less of a concern. (The hull bottom is out of sight. The decks have non-skid as well as fittings which break up the surface so print through doesn't show as easily.)

CoreMat reads notably drier than standard glass so taking the baseline readings on the dry topsides is giving a poor reference in comparison with other laminate areas without CoreMat.
12-27-2009 03:07 PM
TakeFive I have a CT33 coming to me on loan (along with a calibration plate), so I will get to see for myself how well it works.

The benefit of the General Tools device is not so much its low cost, but the "hold" button and audio feedback it gives when trying to locate a peak. Among the several things I want to check out on one of the boats, there is one spot that is not in my line of sight. So the option to reach around a corner, locate the peak via audio feedback, press the hold button, and then look at the reading sounds very useful. But I would need to try it to see if this procedure actually works as well as it sounds.

I may buy the General Tools one from a place with a liberal return policy to compare them side-by-side. Then I'll do some comparisons with the calibration plate and various spacers (to test the effect of the different reported depth sensitivities) as well as some readings on different parts of my two current boats, and see if the two correlate close enough. Hopefully, with the 10 different material calibrations, there will be one that approximates the readings close enough. Like I said, the main interest is in looking for relative gradients to trace the source of leaks. I also realize that there are a whole lot of factors that can lead to false positives and false negatives, regardless of what brand of meter you use.
12-27-2009 12:02 PM
Jasper Windvane Rhythm .. buy the good one. I did , and I love it. Tools are a good investment, especially when you own a boat. Good tools = good job.
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