Locating, Predicting, Preventing and Troubleshooting Power Quality Issues - Upto400 Hz. Higher power frequencies mean smaller and lighter transformers and motors - a critical concern in avionic and military transport applications where weight is a primary concern. Designed specifically for these environments, the Fluke 437 Series II Power Quality and Energy Analyzer is a must-have for those working in ships, submarines, aircraft, spacecraft and other military vehicles. Equipped with all the functionalities of the Fluke 435 Series II, the 437 Series II offers the best in power quality and energy analysis all the way to 400 Hz.