Determine the speaker's positive and negative poles with a multimeter.
First, turn the pointer multimeter to the DC 0-5mA gear, and then connect the two test leads to the two soldering pieces of the speaker to be tested. Press the paper cone of the speaker lightly with your hand, and observe the swing direction of the pointer of the multimeter. If the pointer deflects forward, the red test lead is connected to the negative pole of the speaker, and the black test lead is connected to the positive pole of the speaker. Conversely, the red test lead is connected to the positive pole, and the black test lead is connected to the negative pole.
Use a multimeter to judge the quality of piezoelectric ceramics
Piezoelectric ceramics are a synthetic piezoelectric material. When subjected to external pressure, charges will be generated on both sides, and the amount of charge is proportional to the pressure. This phenomenon is called piezoelectric effect. Piezoelectric ceramics have a piezoelectric effect, that is, they will deform under the action of an external electric field, so piezoelectric ceramic sheets can be used as sounding components.
Utilizing the piezoelectric effect of the piezoelectric ceramic sheet, a multimeter can be used to judge whether it is good or bad.
Lead out two wires from the two poles of the piezoelectric ceramic sheet, then place the ceramic sheet flat on the table, connect the two lead wires to the two test leads of the multimeter respectively, turn the multimeter to the minimum current position, and then press the ceramic sheet lightly with the eraser tip of a pencil , if the pointer of the multimeter swings obviously, it means that the ceramic chip is intact, otherwise, it means it is damaged.
