Dual tracer oscilloscope has two probes, which can measure two signals at the same time. However, the ground wires of these two probes are securely connected with the oscilloscope, so the ground wires of the two probes cannot be connected to two different points of a circuit at the same time, otherwise the two points will cause an electrical short circuit through the oscilloscope. To this end, the earth wire of one of the probes can be removed in the experiment and only one of the earth wires can be used.When two signals need to be observed at the same time, it is necessary to find the common point of the two measured signals on the circuit, connect the earth wire of the probe, and connect the two probes to the signal place, that is, two signals can be observed at the same time on the oscilloscope, and no accident will occur.
This means, of course, that there are other devices in your system whose ground wires are securely connected, as are oscilloscopes.For a homemade system, where the power supply is homemade rather than a dedicated power supply instrument, there are two situations:
The transformer is from the lotus root, so it can not be connected in random. Please pay attention to the measurement, especially when measuring the power supply, or there may be a short circuit hazard of the power line -- oscilloscope ground wire -- safety -- zero line.