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Recalibration of Relative Humidity Probes

#1
Does anyone know where I can get a copy of a procedure to verify the calibration of my relative humidity probes, since the ASTM standard says I need to verify calibration every 30 days?
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#2
(09-12-2008, 05:35 PM)jpeters Wrote:  Does anyone know where I can get a copy of a procedure to verify the calibration of my relative humidity probes, since the ASTM standard says I need to verify calibration every 30 days?

jpeters,
ASTM F-2170 "Standard Test Method for Determining Relative Humidity in Concrete Slabs using in-situ Probes" section 8.2
Rayt
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#3
jpeters,
ASTM F-2170 "Standard Test Method for Determining Relative Humidity in Concrete Slabs using in-situ Probes" section 8.2. contact the manufacturer of the probes and they can give you the particulars on where to send the probes for calibration. With the Wagner RH probes there is no need because they are calibrated at the time of manufacturer
Rayt
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#4
Ray, I have about 10 RapidRH probes that have remained unused for over a year now. Is there any need to send back to Wagner to recalibrate these? If not, how long does Wagner project these will be OK to use as is going forward with no further recalibration? Thanks!
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#5
The RapidRH smart sensors are certified to be calibrated for 2 years from the date of manufacturing. If you purchased your probes after August 2008, the certificate included in the package will tell you what month your smart sensors will expire.

Since you purchased your probes over a year ago, the situation is slightly less clear. If you purchased them directly from Wagner, you shouldn’t have any problem. If they were purchased from a distributor, you might want to contact them to verify that they haven’t sat on the shelf for over the allowed amount of time.
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#6
The Standard Test Method for Determining Relative Humidity in Concrete Slabs using in-situ Probes, then how to test?
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#7
I wouldn’t mess with it. I know a guy who sends his probes in for a cal check every 30 days because he doesn’t have the time or equipment to mess with it. After reading through the ASTM procedure that Ray talked about above, I would do the same thing. I can think of a lot of better things to do with my time then mix up salt solutions or mess with "compressed gas cylinder" every month. Does anyone actually verify their probe's calibration on their own? Maybe it's easier than it sounds.
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#8
Hi Sam,

I ran calibration tests on my Tramex probes, although I felt like the Lone Ranger doing it!! I have been told my probes are the only ones that ever get sent back to the manufacturer..... Hmmmmm, that tells me people aren't checking their probes!

Tramex includes a vial of 75% salt solution. The procedure is to insert a probe into the salt solution vial and place the assembly in an area where it is not subject to fluctuations of temperature, light, and humidity. They suggest a closed drawer. Allow the probe to acclimate for a minimum of 2 hours. The probe should read within 3 percent of 75% RH. If it is not, repeat the test for another 2 hours.

Now let's stop and think about what the manufacturer just told us to do. Put their probe in a salt solution that we know is 75% RH. Let the probe sit 2 hours. (2 hours!!!!!) If the probe doesn't read 72% - 78% (wow, that's a range!) then let it sit for 2 more hours!!!

Now you are expected to take that probe to the field and install it in a hole and wait 45 minutes and trust the reading you get??? C'mon.... What if the probe reads 78%? Is the slab good? Could it be off by 3%? Maybe it is, but the other way!! Maybe the slab is actually 81%!! And we're not testing in a drawer here, we're in an area where air is flowing, sunlight is going across the floor ( readings will change if sunlight warms the probe barrel!)

So I always marked my probes with a sticker showing how far off they were on the last test. Now I had I guys favoring the low reading probes.....

After years of fighting with various probes, I went with Wagner and never looked back. I tested the Wagners every way I could and they always gave consistent dependable results. When I put 6 Tramex probes in a confined slab area (testing purposes) I would get 6 widely spaced readings. 6 Wagners gave me one reading.

I should say, I do not work for Wagner! I am an independent consultant that (in a previous capacity) took advantage of an almost unlimited budget for testing and determining the causes and remedies of flooring failures nationally.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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