What are the advantages of a differential probe over a conventional probe

High pressure differential probe is a kind of probe , It is an oscilloscope probe designed based on the principle of differential amplification , It is one of the mainstream accessories of modern oscilloscope

The differential probe is mainly used to observe the differential signal . Differential signals are cross referenced 、 Instead of using the ground as a reference point . Ordinary single ended probe can also measure differential signal , However, the obtained signal is quite different from the actual signal , Possible “ Ground bomb ” The phenomenon . Besides , In power system testing, it is often required to measure the relative pressure difference between two fires or zero fires , Many users directly use the single ended probe to measure, which leads to the burnout of the probe instrument . This is because the signal common line of the oscilloscope is connected to the protective ground line . The result of this is that everything is added to the oscilloscope , And the signals provided by the oscilloscope have a common connection point . The common connection point is usually the oscilloscope shell through the use of the third wire in the power line of the AC power supply equipment , Connect the probe ground wire to a test point , If a single ended probe is used to measure , Then the ground wire of the single ended probe is directly connected with the power supply line , The result must be a short circuit . In this case , We need a differential probe for floating measurement .

There are two common types of , Class I for low voltage signals , This differential signal is common in high-speed digital circuits , Generally, the amplitude of this kind of measured voltage is ±8V, The bandwidth is generally at 1GHz above . Another type of high-pressure differential probe is specially designed for high-pressure measurement , The measured voltage reaches thousands of volts , This kind of differential signal is common in power supply measurement . The voltage measured by the high-voltage differential probe is generally at KV Level , The bandwidth is generally at 20MHz—100MHz Within the scope of .

The high-voltage differential probe is designed based on the principle of differential circuit , Its measuring voltage is as high as 8kv, The pulse decay time reaches 11ms, It is an ideal tool for surge pulse calibration and measurement , It can effectively protect the oscilloscope from damage when measuring high-voltage pulse . High measurement bandwidth , Completely satisfied EN/IEC61000-4-5 Calibration measurement requirements , It can also be used to measure the clamping voltage of varistor surge protection devices .

Differential signal and ordinary single ended signal wiring comparison , The obvious advantages are reflected in the following three aspects ：

1. Strong anti-interference ability , Because the coupling between the two differential lines is very good , When there is noise outside , Coupled to two lines almost at the same time , The receiver is only concerned about the difference between the two signals , So the external common mode noise can be zui Large offset .

2. Can effectively inhibit EMI, Same thing , Because the polarity of the two signals is opposite , The electromagnetic fields they radiate can cancel each other out , The closer the coupling , The less electromagnetic energy is released to the outside world .

3. Precise timing , Because the switch change of differential signal is located at the intersection of two signals , Unlike ordinary single ended signals, which depend on high and low threshold voltage to judge , So by the craft , The effect of temperature is small , It can reduce the error of time sequence , At the same time, it is more suitable for circuits with low amplitude signals . current LVDS It refers to this kind of small amplitude differential signal technology .

The above is compared with the ordinary probe , What are the advantages of the differential probe