Hi I'm a beginner on using an oscilloscope and I'm sorry if my question may be repeated in other posts. I was working on a circuit with the following materials: (1) an Al plate (5mm thick) (2) a disk-shaped piezo transducer with special electrodes (product note)(product link) (3) two wires (4) a coaxial cable (5) a Tektronix DPO4104 oscilloscope So the PZT was glued on the plate, and wires were soldered on the PZT to connect to the oscilloscope. I tested my setup by knocking the plate, and ended up with sudden voltage rise/drop for the knocks. But I noticed the continuous milli-volt noise signals throughout the whole process. Are they actually noise or something else? How should I reduce them to less than 0.1V as maximum amplitude, or even none? Because I would latter want it to detect 0.3-0.4 V. I've tried scaling, reducing record length, and switching acquisition modes to SAMPLE / PEAK DEFECT / HI RES / ENVELOPE / AVERAGE(with max value possible). But they didn't work. Fig 1. Output Graph Fig 2. Screen picture Fig 3. Parameters of oscilloscope . . . .