One definition of “calibrate” is “to determine, rectify, or mark the graduations of something”. An ammeter is an instrument for measuring electric current. Therefore the simple definition of a calibrated ammeter is a current measuring device marked with units of measure, presumably amperes. In the blower industry, however, the term has developed a specific meaning. A calibrated ammeter is an instrument that measures a blower motor’s current draw and converts the measurement to a display of blower airflow rate.