(07-22-2013 09:09 AM)CC Solutions Wrote: Well here's my take on the thought:
If you were ever called into court to testify that your readings were properly harvested, and you said you caulked the sensor cap down, I could see the question of moisture from the caulk brought up.
I could also see the question of the sensor hole breathing brought up. As the concrete dries the RH goes down, but is your sealed hole allowing the area being measured under the sealed sensor to dry?
I asked Ed and Jason years ago if the holes in the bottom of the sensor were sized to allow the hole to dry out at the same rate as the surrounding concrete and they said they didn't design that type of detail in the probe.
But the probes are not air tight. So what effect does the probe in the hole have on long term readings? If you leave the cap off and the ambient RH is 95%, will the area the sensor reads gain moisture at a faster rate than the slab is gaining at that 40% depth?
Conversely, if the ambient RH is 10% will the hole dry out faster than the surrounding concrete over say a month? Or maybe two months?
And if you seal that hole yourself, how are you impacting the readings?
The same question applies to taping over the probes. Tape will change how the concrete dries at your sensor location.
The answer I got long ago was that nobody has researched the question. Insert fresh probes for the most accurate results.
It would be interesting to place a sealed acrylic box with a sealed divider over two probes in the same slab, and on one side condition the air to 75 degrees and 10% RH and the other side 75 degrees and 95% RH and see if the probes readings vary greatly over a few days. The RH in the slab won't vary in that short amount of time, but would the probe readings?
In other words, what effect does the probe and the permeability of the probe tube itself have on the RH of the concrete the sensor is reading?
CC: Interesting points for sure. As I read your thoughts I'm thinking: If the flanges on the sensors are intended to prohibit moisture from escaping, therefore relying on the bottom side of the sensor to capture readings, then what would be the problem with sealing the cap? After all, the intent is to get the reading from deeper within.
As far as drying, how much true drying takes place in 72 hours? And how much impact does a 3/4" spot have on overall drying?
I could definitely see a lawyer having a field day with this. Lots to consider.
All I know is I've "lost" enough sensors to jobsite abuse and shot blasting BBs, as well as guys putting chunks of drywall inside and replacing the cap (before I started caulking). Have also had countless tests that started out with readings in the 70s and 80s, and dropped to the 50s and 60s.
Jason? Ed? Somebody? What's your take?