Simplify RH Testing – Calibration Tips & Resources

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

Calibration protects you in case moisture problems come up later, and compliance with ASTM F2170 requires calibration and documentation of it.

Any way you look at it, you want to make sure the in-situ probes you use to measure moisture in concrete are calibrated to requirements.

As a reminder, in-situ probes are placed in holes in the concrete slab, at the right testing depth, to measure the RH within it. In-situ RH testing is widely considered the most reliable way to determine the moisture condition of a concrete slab.

What Does Calibration Really Mean?

An in-situ RH 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.

The sensor needs to be properly calibrated before 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 allows more than one way to check calibration, including using a saturated salt solution.

The Wagner Factor – Rapid RH^®

Wagner Meters developed its RH testing products 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, so they’re ready to use right out of the box.

Rapid RH sensors come with a certificate of calibration, the calibration documentation ASTM F2170 calls for.

The Rapid RH L6 Smart Sensor makes it especially simple. Because it’s a single-use sensor, it never needs a calibration check, which makes it a good fit for contractors and flooring installers.

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 F2170 compliance, the calibration of a reusable sensor must be checked within 30 days before it’s reused. Because of the extra time and attention that takes, a single-use system is usually the best choice for most contractors and flooring installers.

To keep those calibration checks simple and quick, Wagner Meters designed the reusable Rapid RH 5.0 Smart Sensor with that process in mind.

Each Rapid RH 5.0 reusable sensor comes with its own patented EasyCare CalCheck™ protective storage unit, which holds a 75% RH salt solution for checking 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 be replaced annually 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 if you prefer a sensor that never needs a calibration check, the single-use Rapid RH L6 is the way to go.

Bottom line: reusable sensors cost more up front and take more time to use and maintain, but they can be used at as many test sites as needed for 12 months before 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 your best option for protecting the integrity of your work. When your work and reputation rest on the results of your moisture testing, a certified, accurate in-situ RH probe gives you the confidence you need.

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Jason Spangler

Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.

Last updated on October 9th, 2026