Test Bridges

Most VTVMs and tube testers have a bridge circuit to give more precise indications.

Bridges have a nich in electronics. Bridges compromise several types, Resistance, Capacitance, Inductance, and Voltage and combinations thereof.

Some of the more sophisticated types can include several modes.
General Radio is THE leader, it has several popular models.
ESI is also a very popular brand.
HealthKit, H.P., FLUKE, TEKTRONIX, there are other manufacturers.

All bridges have two components that are the same precise value, then there is a third component that is adjustable. There is connections that are used to connect an unknown like component.
The indicator is usually a meter that is center balanced pointer.

When the unknown part is hooked up, it completes an electrical unbalance. The adjustable component is a calibrated marked Dial, and the meter itself is either off the center mark to show whether to add or subtract dial markings. The closer the pointer is to the center marked zero, the closer the dial value  is to the unknown value of the component. 
Most bridges have selectable dials to get the correct range. Also most have selectable dials for the type of component to be measured.