Hi from Peru Melanie! I use a Farmex (now rebranded as Agratronix) Mt-Pro and it works well. It doesn't have a native cacao setting so i use the spanish peanuts setting and calibrate it for my beans. its small and portable, not so cheap at around $250 but has proven durable and reliable in the harsh conditions here in Peru
I was looking for a low cost solution.
I found these timber moisture meters on ebay, http://goo.gl/TlAHsX, cheap. I was thinking I could re-position the terminals to cocoa bean size and get an idea of the level.
Anyone tried that?
Can you define what low cost means to you?
Depends on what I'm purchasing, but for this, since its a new hobby I'd say $100 or less would be my max. I would hope to eventually learn how to tell moisture content from organoleptic methods, but a way to determine a control would help.
What do you think of that cheapy thing I posted the ebay link to?
My question was actually to Mel 8-) but glad you asked anyway!
The way the moisture meters work that are above the one you linked to essentially look at the relative humidity that a bunch of beans create in a chamber. This is useful as you're interested in the aggregate humidity of a bunch of beans - not just a single one. Now, the unit you posted uses conductivity between the poles to calculate moisture - i have no idea if it'd work for beans or not - i suspect it'd not work so well for beans with shell on, but to be honest that's just a guess. If it did work, you'd want to perform that test on a hundred beans, and then take the average of them - as noted, knowing moisture of a single bean doesn't really help much. It might work - give it a shot and report back 8-) what you'd have to do is test it with the unit, then dry out each bean individually with an oven/weight loss method to assess how accurate your unit was reading. For $10 i'd say it's worth the trial. Heck, i might even try it (i'm not sure if i've got any cocoa beans around the house or not anymore tho).
The unit Michael linked to, while i have no direct experience with it, according to the video, reports with a +/-2% range - which is a huge range if you're looking to target 6-8% moisture (the vary range itself is 2%).
The best portable one I've ever used is the dickey john miniGAC plus. it comes with 2 calibration curves that are cocoa specific (you may have to download them, i don't recall any longer), and one of them is MUCH more accurate than the other. It's very durable, portable (I've carried one all over the world in conditions you couldn't imagine), and runs, from memory, about $500 USD.