This hand-held unit can be used with any current meter (AA or Mini) and is a direct substitute for a headset or counter. Its crystal based timing circuit counts the revolutions and time, converts them to velocity and displays the results on an easy-to-read LCD display. Special circuits filter the signal, eliminating counting errors. One 9 volt battery provides up to 30 hours of field use. Directly compatible with most Price-type current meters. 16 Character LCD display is good to -30°F.