Often Called A Speedy Meter after the manufacturer -
Calcium Carbide testing is conducted in a sealed pressure vessel using a weighed sample of masonry preferably from the mortar joint extracted from above the damp proof course.
The sample is mixed with a precise measure of calcium carbide powder and inserted in the vessel. This is shaken vigorously and the meter on the bottom provides a reading 0 - 5 - the higher the reading the more moisture is present. The results of this test are very reliable and the meter can often be used to confirm or negate the presence of moisture.