In the usual case, the meter applies a known voltage and measures the current which, by Ohm’s law, gives you the resistance. It is also possible to control the current and measure the voltage ...

The symbol for resistance is R, it is measured in ohms \((\Omega )\). The symbol for current is I, it is measured in amperes \((A)\).

In fact, let’s say they add an ohm of resistance on each leg ... A conventional analog meter makes you zero out the probe resistance by shorting out the probes. But that requires some complexity ...

which in fact refers to -4 dB or -4 VU on the meter. Zero level is the reference level obtained with a 1000 Hz signal and 1 milliwatt of power in a line or circuit of 600 ohms resistance (a 600-ohm ...