When testing moisture content (MC) in concrete, any type of meter or probe must be calibrated to ensure accuracy. Moisture meters for concrete test surface ranges only but can be useful for placing in situ probes for in-depth relative humidity (RH) testing.
In-Situ is a Latin phrase meaning, “in position”. In-situ probes are placed “inside” concrete slabs in order to accurately measure RH. Ideal – except that any moisture meter or in situ probe needs to be calibrated before beginning such assessments. Proper calibration is crucial to accurate RH testing, MC readings, and, logically, successful finished flooring installations.
The Meaning of Calibration
In RH testing, “sleeves” are installed in the concrete slab and then sensors are placed inside these sleeves for relative humidity testing. The sleeve serves to both protect the sensor and to focus the readings at the correct depth in the slab. The sensor inside the probe sleeve then needs to come to the same temperature and humidity level as the surrounding slab – a process called equilibration – before the test proceeds. With a properly equilibrated sensor in the sleeve, contractors can reliably gather test results which reflect the moisture content of the slab in terms of relative humidity as a percentage.
But equilibrated probes are meaningless if the sensor is not calibrated correctly, and so, calibration is a vital first step in the concrete construction process. Before each sensor is even installed in the slab, it is imperative to be sure that the sensor is properly calibrated – that it has met the standard for measuring relative humidity levels. Project documentation often necessitates proof of the calibration process in case the condition of the concrete slab ever should become an issue. Calibration is key both in getting accurate test results and in avoiding possible repercussions in the event of a flooring failure.
The Wagner Factor
Wagner Meters has developed its concrete RH testing product line with a calibration advantage. Wagner’s Rapid RH Smart Sensors are calibrated right at the factory; the moisture meter is ready to go before you receive it. In fact, Wagner Meters provides NIST certification for each sensor, making both your testing confidence and project documentation a snap. The Rapid RH complies fully with ASTM standard F2170-11, which requires moisture meter calibration by rule.
However, equilibrated probes are meaningless if the moisture meter is not calibrated correctly. Wagner Meters’ patented Rapid RH design produces probes that reach moisture equilibrium in about an hour (other industry products can take many hours), faster than any other RH testing. While 72 hours is still necessary for ASTM compliance, having results that quickly means having the ability to make important business decisions immediately.
The Wild Card
Obviously, unreliable RH test results can destabilize an installation schedule. That’s the most prominent downside of purchasing any RH test system without certified calibration. And if the test method makes use of multi-use probes, each sensor must be re-calibrated no more than 30 days before re-use.
This matter of re-calibration can be a logistic nightmare based on time: the currency of any successful concrete slab installation. With an RH test method like the Rapid RH, though, factory calibration and single-use sensors mean that each test system comes out of the box ready to go and fully documentable, at virtually no extra cost compared to multi-use probes.
And equipment cost isn’t the only savings. Where time is a factor, the wait of re-calibration can cause lost crew time and potentially missed deadlines. Working without a key tool is difficult and potentially hazardous to any unsupported moisture content assessments.
The Rapid RH certifies calibration to help contractors certify the integrity of their work. If business rests on the result, a calibrated RH test method is the means of delivery.