Every time I look this up I am being shown how to use a Multimeter. But I want to know WHAT exactly is that multimeter doing? It is looking at the potential difference? But what exactly are the components doing inside. What would the simplest Multimeter look like
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Big secret of the world…. EVERY meter is an ammeter. That is, a meter that reads current, resistance, voltage, power (watts)…. all actually just calibrated in a way to read current, as current is truly measurable. For this example of a volt meter, two leads are connected across the thing you want to measure the voltage of, within those leads is a very large resistor. The trick is to have the resistor significantly higher resistance than everything else in the circuit, so that only an extremely small current travels through the meter, bit the resistance is a known value (say 10k ohms) then by utilizing meter deflection to read amps, a simple equation is used to garner the voltage. (Generally it is Voltage=current x resistance). I say current is the only truly measurable thing because voltage is simply a potential difference between one thing and another, to truly measure that you would have to pick one point, count up all the electrons at that point and calculate the charge, and pick the separate point and do the same, its much easier to connect a known circuit between them and measure how much current flows, because with current flow there is a measurable magnetic field developed which its strength is proportional to current flow. So I can make that field deflect a needle on a meter face, or with fancy digital meters measure the field and spit out actual numbers.
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