Flexible current probe selection guide

Flexible current probe , Rogowski coil . It is an AC current sensor , It is composed of an annular coil and integrator uniformly wound on non ferromagnetic material , The output signal is the differential of current versus time , It can be directly sleeved on the measured conductor to measure the AC current . It is widely used in R & D laboratories 、 Colleges and universities 、 Power grid monitoring 、 Industrial testing 、 Production line, etc , that , How to choose a suitable flexible current probe ？ Which indicators must be paid attention to ？ Today, puke Technology （PRBTEK） Let me share with you ：

1.  bandwidth

Flexible current probe It's an AC probe , Only AC can be measured , Bandwidth has a low-frequency cutoff (-3dB spot )fL And high frequency cutoff (-3dB spot )fH. Here's the picture ：（-3dB spot ： It refers to the actual range 70.7% Location ）

The high-frequency cut-off point of the probe should be considered when selecting the probe fH And low frequency cutoff Whether the requirements are met fL.

Ensure that the amplitude meets the accuracy requirements , Generally, you should leave 5 Multiple allowance . For example, the low-frequency cut-off point of the probe is 50Hz, Indicate the actual measurement 50Hz, The amplitude is about the actual value 70.7%, The error is as high as 30%. That is to measure 50Hz Frequency waveform , Then the cut-off point should be considered to be lower than 10Hz Model of probe . The same is true of the high-frequency cutoff , For example, the driving frequency is 100KHz, To measure accurately , You must select a high-frequency bandwidth greater than 500KHz Current probe , Of course, if you consider the rising edge , Bandwidth should be considered comprehensively . Some current waveforms , Although the frequency is only 100KHz, But there may only be dozens of rising edges ns, You need up to dozens of bandwidth MHz The current probe of .

2、 phase

Flexible current probe Generally, the phase shift is different at different frequency points , The principle is similar to RC Band pass filter , Here's a simple example ：RC High pass filter , Help to understand （ notes ： Online excerpt RC High pass filter diagram ）.

Thus, as shown in the figure RC Approximate frequency characteristic curve of high pass circuit ：

The above analysis shows that ： At the low frequency cutoff RC The phase shift of the high pass filter is 45°, The flexible probe is similar to this principle , Flexible probe is active integral amplifier , The phase shift will be different , The data can be obtained through the manufacturer's actual measurement .

Through the introduction of the above article , Do you know how to choose flexible current probe ？