UT261 series is used for determining 3-phase power phase sequence, missing phase indication, and motor phase  rotation (UT261B). UT261A and UT261B can measure AC voltage of 40~700V and 90~600V respectively.  These devices can operate in frequency range of 15~400Hz. UT261 are durable devices which can withstand impact from 2 meter’ s height. Test leads with protective tubing are included in optional accessories.