Piezoelectric ceramic speaker detection method

1 check from the appearance 

     Piezoelectric ceramic speakers, also called crystal speakers, mainly the surface of the piezoelectric film without damage, cracking; whether sealing off the lead, Weld. 

     2 "piezoelectric effect" test 

     It is not easy to measure with a multimeter DC resistance, but can skillfully use the "piezoelectric effect" inverse procedure to detect. The multimeter placed microamps block, two tables stick regardless of positive and negative connected to the poles of the piezoelectric chip lead, then gently press with a pencil eraser head flat on the desktop or piezoelectric glass platen, observe whether the header pointer swing. If a significant swing hands, indicating that the piezoelectric sheet intact, otherwise the piezoelectric chip failure.