Simplify RH Testing – Calibration Tips & Resources

Relative humidity (RH) moisture testing in concrete requires a properly calibrated in situ probe to ensure accuracy.

Calibration certainly makes good sense for your own protection in case any moisture-related issues arise in the future. In addition, compliance with ASTM F2170 certainly requires calibration and its accompanying documentation.


So any way you look at it – you want to make sure the in situ probes you’re using to measure moisture in concrete are calibrated to requirements.

Just a quick reminder: in situ probes are inserted down into the concrete slab to measure the RH within it, which is the only scientifically proven way to verify the moisture condition in concrete.

What Does Calibration Really Mean?

An RH in situ probe has two main components: a sleeve and a sensor. The sleeve is installed in the concrete slab. The sensor is placed in the sleeve for performing the actual RH test. The sleeve protects the sensor and helps with proper equilibration for the most relevant RH reading.

However, the sensor needs to be properly calibrated prior to use. Calibration ensures that the sensor will provide sufficiently accurate relative humidity measurements to meet the ASTM F2170 standard for relative humidity testing. ASTM F2170 outlines two different options for calibration methods, including using a salt solution.

Rapid RH L6 and 5.0 Sensors

The Wagner Factor – Rapid RH

Wagner Meters developed its RH testing product line with easy calibration in mind. Its Rapid RH® Smart Sensors—both the Rapid RH L6 and the Rapid RH 5.0— are calibrated at the factory, which means they’re ready to use right out of the box.

In fact, Wagner Meters provides a NIST certificate for each sensor, attesting to its calibration. The NIST certificate is the calibration documentation needed by ASTM F2170.

Nothing could be simpler, especially when you use the Rapid RH L6 Smart Sensor, which is a single-use sensor that provides you with all the calibration functionality and documentation you’ll ever need. No calibration check is ever needed. Because it is so fast and simple to use, the Rapid RH L6 is especially well suited for contractors and flooring installers.

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Maintaining Calibration for Reusable Sensors

In contrast to the Rapid RH L6 Smart Sensor, which is designed for use at one test location, a reusable sensor can be used at multiple test locations. After it’s installed at one location and the reading is taken, it can be removed and installed at another location.

For some building inspectors, flooring inspectors, engineering firms, and some QC personnel, a reusable system such as the Rapid RH 5.0 may make sense.

However, to maintain ASTM compliance, the calibration of any reusable sensor must be checked no more than 30 days before it is reused. The additional time and attention required to ensure proper calibration means that a reusable system is usually the best choice for MOST contractors and flooring installers.

Because of the extra time needed to perform calibration procedures, Wagner Meters has designed the reusable Rapid RH 5.0 Smart Sensor to make the process as simple and quick as possible.

Each Rapid RH 5.0 reusable sensor comes with its own patented EasyCare CalCheck protective storage device that includes a salt chamber to check calibration.

The EasyCare CalCheck storage chamber protects and stores the Rapid RH reusable Smart Sensor under optimal conditions. This both extends the life of each sensor and greatly reduces the time needed to check calibration.

Free Download – Which Rapid RH Sensor is Right For You?

Each Rapid RH 5.0 sensor must have an annual replacement with a newly certified sensor to maintain ASTM F2170 Compliance.

The innovative design of the Rapid RH 5.0 makes it a great choice for anyone who prefers using a reusable RH sensor. And for anyone who prefers the ease and simplicity of a sensor that never requires checking calibration, look no further than the Rapid RH L6. That’s because calibration checks and recalibration are not needed with its single-use system.

Bottom line: ANY reusable sensors have a larger initial investment, require more time to utilize and maintain, but can be used in as many test sites as necessary for a 12-month period, prior to any additional investment.

More important than the type of sensor you choose is the choice you make about which test to employ.

Remember: RH testing is always your best option to protect the integrity of your work. When your work and reputation rest on the results of your moisture content testing, a certified, accurate RH in situ probe delivers the confidence you need.

Last updated on May 30th, 2024


  1. Ryan says:


    I am attempting to check calibration on our rapid RH 5.0 sensors. I am using the datamaster app along with the Bluetooth device and getting a failed calibration message when using the NaCl setting for calibration. However I understand this is not necessarily a big deal and that the sensor and the bluetooth device may simply have to come into equilibrium? Can I just leave the bluetooth device in the sensor and then check again in a few hours? Thank you.

    • Jason Spangler says:


      Thanks for the question. This is best done via phone. Give me a call when you have time at 800-634-9961 X235.


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