### Measuring resistance by comparison

As per Ohm's law, current through a conductor is proportianl to the
voltage across it. If both voltage and current are known, resistance can
be calculated. An unknown resistance can be measured by comparing the
voltage drop with that of a known resistor. Figure shows a 1k resistor
from IN1 to Ground and an unknown resistor from PVS to IN1.

Voltage applied to PVS = 4.0 volts

Voltage measured at IN1 (across 1k
resistor) = 1.254

Current = V/R = 1.254/1000 = 1.254 mA . The same amount of current
flows through the unknown resistor.

Voltage across the unknown resistor = 4.0 - 1.254 = 2.746 volts

value of the unknown resistor = 2.746 / 1.254 = 2190 Ohm