+- Concrete Moisture Measurement Forums (http://www.wagnermeters.com/concreteforum)
+-- Forum: Concrete (/forumdisplay.php?fid=1)
+--- Forum: Rapid RH Q&A (/forumdisplay.php?fid=5)
+--- Thread: false high test results (/showthread.php?tid=214)
Pages: 1 2
false high test results - eaadams - 10-25-2011 08:57 PM
I had a testing firm (very reputable) tell me today there is a way that Wagner rapid rh can get a false high. He said that residual dust can cause a false high reading.
On my next set of tests I'm going to have the tester poorly clean out a test site hole and do a normal test hole next to it. Should tell me an answer.
Does dust in the hole cause a high reading?
RE: false high test results - rapidrhrep - 10-26-2011 11:10 AM
EA:
Our webinar actually touches on this. The testing company you spoke with is inaccurate. The dust will not cause a false high overall. The dust MAY slow the equilibration of the probe in the hole. These two explanations are very different. Bottomline, it is important to get that hole clean so you can take full advantage of all of the positive things the Rapid RH brings to the table.
Thanks,
Jason
RE: false high test results - eaadams - 10-26-2011 12:11 PM
Is the webinar different from the YouTube videos?
RE: false high test results - Ernesto - 10-26-2011 04:47 PM
Shouldn't the dust settle after 12 or 24 hours? Is it the dust on the senors that can do it? I don't see how there can be zero dust when your shoving a sensor down a hole thats tight anyhow. It has to make some dust. Can you put a video camera in a hole for us to check and see Jason?
RE: false high test results - eaadams - 10-26-2011 05:21 PM
ernesto - I think that is what Jason is saying "The dust MAY slow the equilibration of the probe"
RE: false high test results - rapidrhrep - 10-26-2011 07:05 PM
@EA Not all of the webinar video segments are posted on the website.
@ernesto I think I'm going to pass on trying to McGyver a camera to go in the hole.
Bottomline: Clean out the hole properly and the equilibration rate will be much better.
RE: false high test results - eaadams - 10-26-2011 07:11 PM
hrm ok I'll break down and do the webinar then...
I had assumed it was the same as the Youtube vids.
I saw a camera used recently to scope a drain that was depositing rain water into a slab. Oh what a disaster.
RE: false high test results - Ernesto - 10-26-2011 07:17 PM
(10-26-2011 07:05 PM)rapidrhrep Wrote: @ernesto I think I'm going to pass on trying to McGyver a camera to go in the hole.
Bottomline: Clean out the hole properly and the equilibration rate will be much better.
Of course, a clean hole is a happy hole.
But you could camera up the bottom of a hole drilled in a say 4 " x 2' x 2' slab. I bet if you call up Howard K he might have some laying around. Think utube. You could show us the diff between a dirty hole vs a cleanly scrubbed hole.
RE: false high test results - eaadams - 10-26-2011 09:43 PM
ERRR if you can't figure it out w/o a camera it is inapplicable in the real world.
RE: false high test results - CC Solutions - 10-28-2011 11:47 AM
Easy solution, pour concrete using glass as the aggregate and you'll be able to see the bottom of the hole.
Realistically, and correct me if I am wrong Jason, dust is bad for several reasons. Lots of dust can pack in around the sensor, keep the probe from reaching the bottom of the hole, and take up airspace. We'd have to think about if the dust were completely dried out from the drilling process and it sits in the bottom of the hole, it would act as a sponge (BOB!!) that could conceivable affect readings, for sure in the short term.
The proper procedure is to vac the hole, scrub it with a wire brush, vac and repeat until the hole is clean. Clean = no dust.