se a multimeter to determine the positive and negative poles of the speaker
First, turn the pointer multimeter to DC 0~5mA, and then connect the two test leads to the two solder lugs of the speaker to be tested. Lightly press the paper cone of the speaker with your hand and observe the swing direction of the pointer of the multimeter. If the pointer is deflected 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. On the contrary, the red test lead is connected to the positive electrode, and the black test lead is connected to the negative electrode.
Use a multimeter to judge the quality of piezoelectric ceramics
Piezoelectric ceramic is 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 the piezoelectric effect. Piezoelectric ceramics have the piezoelectric effect, that is, under the action of an external electric field, deformation will occur, so piezoelectric ceramics can be used as sound components.
Using the piezoelectric effect of the piezoelectric ceramic sheet, a multimeter can be used to judge its quality.
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 leads to the two test pens of the multimeter, turn the multimeter to the minimum current block, and then lightly press the ceramic sheet with the eraser tip of a pencil. , If the pointer of the multimeter swings obviously, it means that the ceramic piece is in good condition; otherwise, it means that it is damaged.
