Q10Electronic Measurement & Instrumentation

Both are types of AC potentiometers, but they define the voltage vector differently:

- Polar-type Potentiometer (e.g., Drysdale): Measures the unknown voltage directly in polar form ($V\angle \theta$). It uses one slide wire for magnitude $V$ and a phase-shifting transformer to determine the phase angle $\theta$.

- Coordinate-type Potentiometer (e.g., Gall-Tinsley): Measures the voltage in rectangular coordinates ($V_1+j{V}_2$). It contains two separate potentiometers: one measures the in-phase component ($V_1$) and the other measures the quadrature component ($V_2$, exactly $90^{\circ }$ out of phase).