Short Circuit tester

[Tarot Superstars]

Hello.
I have seen a short circuit tester made with 3 * 9V batteries, a voltage limiter component and a resistor connected to the probes of a multimeter.
The theory is that the meter becomes sensitive enough to read very low resistances and the lowest resistance to ground on a circuit is likely to be a short circuit in that area.

Link
The Amazing $1 Short Finder Upgraded! Convert ... - YouTube
https://www.youtube.com/watch?v=0eixDdCpiO4

My multimeter isn't normally sensitive to very small resistance, but when I put a 1 mega ohm resistor in series with one of the probes the meter now shows the difference. I think it's about 1/1000 th of an ohm or more.
I don't have the meter or the circuit for the 1st design so I can't tell you the exact values. So, then I see the very small differences between the resistance to each component on a circuit.

My question is, is my method good enough?
Do I need to add the batteries as was in the first design and the voltage regulator component (I think it was a LM317)?
Any advice is appreciated.

[stj]

Re: Short Circuit tester

if your putting more than 1 or 2 volts into the board your risking damaging some components

[hcs77]

Re: Short Circuit tester

Many RAM, ROM, SOC, etc ic datasheets contains an absolute maximum ratings for voltage, for 5V SRAM is VCC+0.3V. This is a theoretical upper limit.
If you want to find internal connection in the pcb (eg. reverse engineering), a simple way to connect 2 schottky diodes antiparallel to the multimeter probe. This will limit the multimeter output voltage to a safe level, 0,2-0,3V. You can use silicon diodes like 1n4001, but it gives a bit higher voltage.

[Tarot Superstars]

Re: Short Circuit tester

Hello.
I have seen a short circuit tester made with 3 * 9V batteries, a voltage limiter component and a resistor connected to the probes of a multimeter.
The theory is that the meter becomes sensitive enough to read very low resistances and the lowest resistance to ground on a circuit is likely to be a short circuit in that area.

Link
The Amazing $1 Short Finder Upgraded! Convert ... - YouTube
https://www.youtube.com/watch?v=0eixDdCpiO4

My multimeter isn't normally sensitive to very small resistance, but when I put a 1 mega ohm resistor in series with one of the probes the meter now shows the difference. I think it's about 1/1000 th of an ohm or more.
I don't have the meter or the circuit for the 1st design so I can't tell you the exact values. So, then I see the very small differences between the resistance to each component on a circuit.

My question is, is my method good enough?
Do I need to add the batteries as was in the first design and the voltage regulator component (I think it was a LM317)?
Any advice is appreciated.

I quoted the voltage incorrectly. It's 3 x 1.5 V batteries in series.

[stj]

Re: Short Circuit tester

that's still too much for modern 3.3 or 1.8v parts
the multimeter already outputs 2-3v

[RetroComputingGrotto]

Re: Short Circuit tester

3*9V batteries could be 27V which is far too high! In the video you linked to, Learn Electronics Repairs uses 3*1.5V giving a max of 4.5V.

Don't modern CPUs run at 1V so even 4.5V probed in the wrong place could zap a CPU?

[stj]

Re: Short Circuit tester

1.8v is common, but yes - some stuff like cpu/gpu cores are even less