The DPQ are used for power factor (cos φ) measurement. There are versions for single-phse and three-phase AC, for balanced or unbalanced load. Versions …/2 are suitable for lines with or without neutral. The frequency is 50 or 60 Hz. The DPQ../3, are used a moving-iron quotientmeter.  They are also equipped with eddy-current damping, pivot suspension and spring-loaded jewel bearings (without spring for DPQ…/3) for vibration and shock resistance. DPQ types have neither mechanical restoring torque non zero adjuster. Therefore, the pointer has not a determinate position when the instrument is disconnected.