What is the working principle and main function of the high voltage differential probe?

The differential amplification principle of the high-voltage differential probe is that a pair of signals are simultaneously input into the amplifier circuit, and then subtracted to obtain the original signal. The differential amplifier is an amplifier composed of two transistors with the same parameter characteristics using direct coupling. If the two input terminals are respectively input with signals of the same magnitude and phase, the output is zero, thus overcoming the zero drift.

High-voltage differential probes can convert floating signals between any two points into ground signals for use with oscilloscopes, electric meters, or computers. Many circuits, especially motor circuits, contain DC offset (DC OFFSET) or AC offset (AC OFFEST) or even no ground loop at all. In this case, rashly using an oscilloscope will cause electric shock, damage the oscilloscope, or cause a fire in the wires. In this case, the only better choice is to use a differential probe.

Among the common differential probes, there is a type that is designed for low-voltage signals. This type of differential signal is more common in high-speed digital circuits. The common amplitude of the measured voltage of this type of differential probe is ±8V, and the bandwidth is generally above 1GHz. The other type is specifically designed for high-voltage measurement, with a measured voltage of up to KV. This type of differential signal is more common in switching power supply measurements. This type of differential probe is called a high-voltage differential probe. The measured voltage is generally at the KV level, and the bandwidth is more commonly in the range of 20MHz-100MHz.

Differential probes are mainly used for measuring floating ground systems. In power system testing, it is often required to measure the relative voltage difference between the live wire and the live wire, or between the live wire and the neutral (neutral) wire in the three-phase power supply. Many users directly use single-ended probes to measure the voltage at two points, which often causes the probe to burn out. This is because: the "signal common line" terminal of most oscilloscopes is connected to the protective grounding system, which is usually called "grounding".