The application scenario is current sampling driven by motor servo，This is the diagram：
Encountered two problems：
- There are burrs in the current sampled by the software when the motor is idling。
- The sampling current of software is larger than that of oscilloscope when servo load。
|
oscilloscope current（max） |
The current sampled by the software（max） |
error |
|
15.35 |
16.1196 |
0.7696 |
|
24 |
25.79136 |
1.79136 |
|
30 |
32.2392 |
2.2392 |
二、Actual schematic diagram
The power supply：
The current sampling：
三、The current solution
Change the R19 resistor to 1Ω，After modification, the sampling burr disappeared and the sampling was accurate。
This is the graph and the data：
|
oscilloscope current（max） |
The current sampled by the software（max） |
error |
|
16.25 |
16.1196 |
-0.1304 |
|
25.9 |
25.79136 |
-0.10864 |
|
32 |
32.2392 |
0.2392 |
Questions：
1.Why does changing the resistance make the current sample correct？
- Why is R19 resistor still needed for differential sampling？
If the picture is not clear, You can read the document。
The current sampling problem.docx
