External Power supply current limit set to MAX amps to find SHORTS on a PCB

[Diver300]

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What kind of short are u talking about?
Why would it be in the millivolts?

Do you mean, measuring from VCC to ground on each IC chip and what component is connect to the VCC and ground rails?



So how do u know where the short is? there is NO voltage drop from VCC to ground on that component?

The techniques relies on there being some voltage drop along the power lines. It will be very small, which I why you need to measure millivolts or fractions of millivolts.

It is not measuring the voltage across the component or short circuit.

 

[KeepItSimpleStupid]

What you might not understand is that everything on the PCB, including the PCB itself is a component. The PCB is a parallel path. The traces have resistance, capacitance and inductance. That's just the way it is.

A broken trace, say 1/4" apart in free air is an open until somebody puts 60 kV across it.

Zero and infinate are very difficult numbers to obtain sometimes. 0 resistance is impossible to obtain,, just like 0 Kelvin.
Zero as a floating point value in a computer may also be a difficult number to obtain.

I've worked on boards where a "fingerprint or the oils left by your finger" rendered it unusable until cleaned.

The oild left by a fingerprint in a UHV (Ultr High Vaccum) system eds up showing up as a virtual leak. It's not a leak at all, h=jut the fingerprint outgassing. UHV is, below 1e-7 torr: https://en.wikipedia.org/wiki/Ultra-high_vacuum

Repeat:
There is no such thing as zero resistance.
OPEN and SHORT are relative concepts. You might be better using OPEN PATH and THE SHORTEST PATH.
Nearly every thing from the PCB to the wires are "components". They have the basic properties of resistance, capacitance and inductance.

 

[cowboybob]

Let's try this again...

 

[Ian Rogers]

Thread closed...