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50% fail rate

#2
Thanks for your question. Here is Rapid RH Product Specialist, Jason Spangler had to say:

First of all, I would never state “false positive”. The sensor is reading the environment it is installed into. What is there to say, based on the way you state in your question, that there isn’t a 50% “false negative” rate? With that being said, if they are using Rapid RH 4.0 throughout these could be some of the culprits:
1- Depth of hole is critical. Too deep, higher RH% and vice a versa.
2- How well is the hole drilled. Improperly drilled holes will lead to the sensor not sealing properly.
3- Variances in truckloads of concrete. Remember, this is why we are testing every 1000 sqft.
4- Drilling directly into aggregate. If there is a large piece of aggregate that has been drilled into at the bottom of the hole, this is what the Rapid RH 4.0 will read, usually low.
If they are using competitive products(besides the two you mentioned):
1- Sleeve design may be allowing sidewall RH down into the hole, thus giving a lower “average” RH as opposed to the true RH at 40% depth.
2- How high up in the hole does the sensor live? You may be drilling to 40% depth of the slab, but where is that sensor actually living and reading from? The higher it sits up in the hole, the lower the reading.
The question didn’t really give me a lot of specifics to work with, so I made some assumptions. Another think to think about, per ASTM F2170, all sensors are in conformance as long as they are +- 2% from 50-90%RH. This could account for as much as a 4% variance from sensor to sensor with all other conditions being equal.
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Messages In This Thread
50% fail rate - eaadams - 05-27-2011, 10:55 AM
RE: 50% fail rate - EWagner - 05-27-2011, 03:55 PM
RE: 50% fail rate - eaadams - 05-27-2011, 04:57 PM
RE: 50% fail rate - CC Solutions - 05-30-2011, 11:18 AM
RE: 50% fail rate - eaadams - 05-30-2011, 01:24 PM
RE: 50% fail rate - CC Solutions - 09-12-2011, 05:43 PM
RE: 50% fail rate - eaadams - 09-13-2011, 03:07 PM
RE: 50% fail rate - CC Solutions - 09-13-2011, 05:44 PM
RE: 50% fail rate - eaadams - 09-13-2011, 05:50 PM
RE: 50% fail rate - CC Solutions - 09-13-2011, 05:58 PM
RE: 50% fail rate - eaadams - 09-13-2011, 06:01 PM
RE: 50% fail rate - CC Solutions - 09-13-2011, 06:04 PM

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