Thread: Moisture meter jumps between two readings

A simple case of poor contacts! As a one-time radio tech, I should've thought of it immediately - in the early transistor radio days "dry" solder joints on the printed circuits causing intermittent faults were a common occurrence (& sometimes very difficult to locate).

I'm glad you sorted it out - like NC Archer, I can now get a good night's sleep...

Cheers,

Originally Posted by IanW

A simple case of poor contacts!

Im not convinced it's a contact problem.

There is about the same force needed to push pins into the holes whether the holes are in endgrain or across the grain. In both cases the pins make good contact. I have to yank the meter quite firmly to get the pins out.

When I just push the pins (no holes and even lightly) into the end grain of any other wood in the shed (jarrah, spotted gum, tassie oak, sheoak etc) the pins hardly penetrate into the wood but all these readings are always steady.

OK, I'm back to being thoroughly puzzled. From my first reading of post #15, I interpreted it that you'd drilled cross-grain holes to get deeper penetration (= more secure contact) & that gave you stable readings, but on re-reading more carefully, it seems you just measured across the grain on a face instead of along it.

I can come up with a tentative theory for why electrical conduction along the fibres might be different from from measuring it at 90 deg to the fibre orientation, & that is that the drying regime has pulled all the free water out of the cell walls (increasing resistance of the cell wall), but there is some residual water in the old cell cavities, i.e. the (water) conducting channels. These would provide some electrolytic fluid to conduct along the fibre direction, but it would only help in small. separate pools between the cell walls when the current is trying to move across the grain. However, it's hard to see why it would be intermittent at what looks like a fixed frequency unless there is some capacitance-coupling across the poorly-conducting dry cell walls, but that's getting really wild & theoretical......

Might have to remain one of those life mysteries. Pity you're not still in your old role - it could be a good project for an honours student....

Thanks Ian. I do like your theory but both measurement cases are a form of cross grain measurement. The difference is one method is into the ends of the grain, while teh other is into the sides of the grain.

If I'm not careful nI can see this consuming inordinate amounts of y time so I'm going to call it quits and just use the stable readings for now.

Originally Posted by BobL

.......If I'm not careful nI can see this consuming inordinate amounts of y time so I'm going to call it quits....

Like I said, you need an honours student!.....