Circuit Fundamentals Simulator

Swipe the diagram sideways to see all of it.

Swipe the diagram sideways to see all of it.

• Set it up: two meters, one on ohms and one on volts, both sets of probes on the same two points.
• What you will see: the volts meter reading a voltage the ohms meter is making.
• Why it matters: proof, in a number you took yourself, that the meter is the source.
• And why power off: anything else feeding those two points adds to a voltage the ohmmeter thinks it made.

Swipe the diagram sideways to see all of it.

• Set it up: the same two meters, plus a third broken into the path on mA.
• Meter 3 reads the current the ohmmeter is sending.
• Meter 2 reads the voltage that current makes across the part.
• Divide one by the other and you land back on meter 1’s reading — near enough, on two displays rounded to three figures. That division is all an ohmmeter ever does.
• Watch the mA jack: an ammeter is wired into the circuit, never across it.
• These are one bench’s readings, and they are smaller than the panel above — putting the ammeter in the path changes what the ohmmeter is driving, so its test current changes too. Expect your own meters to read something else again.

Swipe the diagram sideways to see all of it.

• The answer is printed beside the part, so what you are really checking is the meter and your own technique.
• Each one sits on its own pads, with nothing else wired to it — so there is no supply to switch off first.
• A real circuit is never like that: power off and the part isolated, or you are measuring the rest of the vehicle too.

Swipe the diagram sideways to see all of it.

• Same rules as above: power off, the part isolated, either lead on either end.
• What is new: the leads are across more than one resistor at a time.
• Work it out before you measure. A reading that disagrees with the arithmetic is how you find out the circuit is not wired the way you thought.