The C555 sensor pad that emits the electromagnetic signal measures 2.0-inches (50mm) wide by 2.5-inches (63mm) long. This entire surface should be fully contacted with the material you are scanning. Bumps, ridges, and other raised areas will disrupt full sensor pad contact and will cause the C555 to give inaccurate or potentially misleading data. You may find it useful to use rough grit sandpaper or another abrasive grinding system to create smooth areas of concrete to scan with the C555 for the most accurate readings. In the Standard Measurement mode, the C555 measures moisture within a 1% to 6.9% moisture reading range. The C555 also features a Relative Measurement mode which will give you a comparative indication of moisture in other materials than concrete with a numerical scale from 1 to 100. However, all measured surfaces should be smooth to ensure the most accurate readings.
The C555 features an alarm audio sound that corresponds to a high moisture content alarm threshold, within the Standard Measurement mode, and programmable to sound the alert at readings from 0.0 to 6.9. This function is perhaps most useful when scanning a section of concrete to locate higher moisture content areas without continually looking at the digital display.
If you are ever unsure whether the C555 Concrete Moisture Meter is calibrated, an On-Demand Calibrator platform is included to allow the user to calibrate the C555 back to original factory standards in less than a minute. The calibration process is simple and fast so that the user can very quickly get back to using the C555 with as little delay as possible.