Why Zero Ohms Resistor?

I always wonder the uses of zero ohms resistor, maybe you had too. As we know resistor were used in circuits simply just to oppose the flow of electrical current. It has the value that determined by the color of band on resistor body. You may not need this resistor when building the circuits on the breadboard, but sometimes we could find this zero ohms resistor in commercial circuit such a microcontroller circuit.

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Zero ohms resistor can be a wire wound type or surface mount type; it all depends on the boards. Any type could be adapted to the circuit as long as it does the job well. Keep in mind, this resistor different with current sense resistor since this current sense resistor attached to “sense” the amount of current being used by the load.

Picture by Wikipedia

 Most of zero ohms resistor is available in 1/4Watt and 1/8Watt power rating, and generally marked with a single black band. Due to the fact resistor has a tolerance value. In other word, it still has some internal resistance which is very small like as 0.005ohms and it can be neglected at all.

Why zero ohms resistor used on circuits?

No exact answer for this as it depends on variety reasons. Why we don’t just use a common jumper wire like we do on breadboard since it's just like a simple “conductor”?
There are many reasons behind this question.

The common reasons are:
1.    Most of manufactures use a machine that automatically inserts the components on the boards. That is not an easy job to produce a thousand even a million boards manually. In some cases, they need to connect two points on the printed circuit board and the downside is an automatic machine couldn’t “grasp” the jumper wires. Please never imagine manufactures will insert the jumper wires manually. The other reason is the two points that connected with zero ohms resistor could be used as a test point to measure the current during development and testing.

2.   The engineers have a plan to change the resistor if devices don’t work as their calculation. This will give a flexibility to remove that zero ohms resistor and use more reliable components on printed circuit board.

3.    Saving cost, yes you hear it right. The printed circuit board, especially single sided board is much cheaper than double sided board and that is one of reason to use this resistor as a jumper wire. Double sided board uses a vias to connect the traces and it can’t be applied to a single side board.

4.    For a good looking printed circuit board. The circuit board needs to look neat and inability to connect some points on PCB due to other circuit paths make the designers have to use this zero ohms resistor as well.

Well, at least the circuit boards are still working well and we don’t have a problem with zero ohms resistor. Electronics just like a puzzle and it was fun to learn all about that. If you have some thought, I would like to hear from you.

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