The title should cause some sparks, no pun intended.
It really is a bold assumption - that we can summarize every electrical problem in the history or future of electronics down to one single reason.
I will stand by the statement, but there is an unfortunate flip side...
Just because there is one single cause, that does NOT mean there is one single solution. In fact, there are millions of possible scenarios, therefore millions of possible fixes that must be implemented.
But I won't give away the reason this early.
First, we'll discuss a few of those scenarios, starting with some easy ones.
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Troubleshooting a failed motor
You test the motor and the windings appear functional. Insulation tests good with a megger. So you back up and look to the motor starter.
In the starter, you find that an overload in the motor had caused a slight over-current, tripping the magnetic overload relay.
The problem is cleared from the machine, the manual reset button is pressed, and power is restored.
Problem solved.
Flying wires on a terminal block connector
After testing a couple of wires, locating a bad sensor, and replacing the sensor, power is restored to the control cabinet. Suddenly, a large spark from the DIN rail terminals so power is quickly shut off again.
On inspection, there appears to be a single strand of copper from the negative voltage wire that is barely sticking out and touching a live + voltage wire next to it.
The wire is re-trimmed and a ferrule crimped onto it. The terminal block is replaced with one that isn't burned, and after a bunch of wasted time...
Problem solved.
Newly networked VFD keeps faulting out
A new Variable Frequency Drive has replaced a soft starter. At first, it was driven with direct digital inputs, but then later is switched to an Ethernet network control.
Every once in a while, a fault appears. It seems to be connected to a drop-out in network signal, resulting in a default 'OFF' command and a fault condition.
The problem is finally traced to a network drop-out every time a particular motor starts or accelerates. The Ethernet cable nearby is experiencing interference, common with motors and inductive sources.
The cable is re-routed safely away from the motor and replaced with a shielded Ethernet cable.
Problem solved.
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Each of these problems was unique, but they had one factor in common.
Here it is - the cause of every electrical problem ---
A change in resistance.
Every electrical problem is rooted down to an unexpected (and often harmful) change in resistance.
If the symptoms appear as excessive heat, and even burning material, and then finally the whole system shuts down. The cause: a component dropped in resistance (perhaps even a short-circuit) which raised current to a harmful level.
If the symptoms are a total lack of any sort of current, effectively a dead circuit, the cause is that somewhere, resistance in the circuit has jumped to an extremely high 'Open' level.
Even problems with inductive and capacitive interference common in communication signals arise from a lowered resistance at higher switching frequencies. This lowered resistance causes slight current and voltage spikes in the wires, interpreted as incorrect signals.
Does the statement seem to be overly simple? Perhaps.
It does sound like the problems should be easy to solve, and that's not always the case.
But here's the main reason for making such a bold statement - troubleshooting is ALWAYS easier when you can break the process down into small, consistent steps, each component playing unique roles, yet only changing one property of the circuit.
Every component simply changes the resistance.
An open switch stops the flow of electricity... Very, very high resistance.
A closed switch allows a lot of current... Very, very low resistance
A load device limits the flow of current... Some resistance
Load current suddenly increased... Resistance must have dropped
A short circuit caused a big spark... Resistance suddenly dropped to zero
A relay output doesn't seem to turn ON... Resistance must be stuck very, very high
A solid-state relay generates too much heat... The contacts must have too much resistance
Measuring the output of a sensor only gives 16 volts instead of the expected 24? Too much resistance inside the sensor
If you want to locate problems, you really need to be good at using the available tools.
If this is true, that every problem is related to resistance, a voltmeter is a VERY effective tool for tracking down nearly every problem.
Is this ever inaccurate?
Well, maybe in a few cases.
For high-frequency switching and communication, voltmeters aren't very useful.
Also, for IT-related problems, such as an incorrect IP address, that's a software problem and a voltmeter won't be of any use.
But if you want to be good a troubleshooting, here is one piece of advice:
--Understand how voltage changes point to resistance changes--
If you understand this, you will become VERY good at locating problems.
Finding and fixing problems faster saves a lot of money.
Every company likes someone who can save them a lot of money.