Different gnd polygon question

[Karamel]

Hi,

I have a one question about pcb design.

Below, there is a pcb which i have found it from aliexpress. You can see clearly that, pcb has a different gnd polygon. Gnd pad was not connected directly. This was connected with wire which located inside gnd polygon.

What is meaning of that? Why did it use?

[ThomasDK]

My guess would be that it is used as a crude current sensing resistor.
What's on the other side?

[Karamel]

I guess not.  maybe i am mistaken. I dont know.

http://tr.aliexpress.com/item/5pcs-lot-DC-DC-step-up-down-power-supply-Converter-voltague-regulator-LM2596-LM2577-DC-35V/1996705981.html

[T3sl4co1l]

In cheap Chinese products, there is often no accounting for purpose or reason...

Often, slotted conductors will be used to push current flow into component pins, like a filter capacitor or shunt resistor.  That wouldn't make much sense here.

If it is being used as a shunt, that's even worse, because copper has quite low resistance and high inductance, and a terrible tempco.  So the DC voltage drop is small and extremely drifty, and the AC voltage drop is dominant at switching frequencies.

Tim

[Karamel]

Hi tim. Thank you so much for your replying.

Could you show and explain any slotted conductor application? I am an electric engineering student who is attending 1st year. Sometimes, i cannot understand cleary.

Best regards.

[Karamel]

Could you support your knowlage with documents or pictures? Which book do i have to read for learning this stuation?

[djQUAN]

It is commonly seen in chinese DC-DC modules used as current shunts. Yes, it is highly inaccurate and has a high TC but it is essentially free and (sort of) does the job so they do it.

I have those CC-CV chinese modules and I traced them out so they are indeed used as shunts.