The REOTEMP Soil Moisture Meter gives you the a relative wetter than or dryer than reading of your compost or soil sample by means of a sensor in the bottom of its 17 probe. Easy to operate, just insert the probe into the medium for immediate results. Keep in mind that only the tip of the probe is sensitive and the material being tested MUST come into direct contact with it to obtain accurate readings. Easy to calibrate, readings scale 0-10. Durable, heavy duty, all metal construction. Uses one AA battery.