The Megger TRS1D Transformer Ratio Standard is a unit designed to be used with ratio meters as a high accuracy reference ratio standard. This unique standard is able to provide ratios in step down (traditional ratio test instruments) test mode. The standard is designed for use as a laboratory calibration standard, or as a portable check standard for field ratio and phase verification of any ratio instrument. The TRS1D can be used with any single phase and three phase ratio meter. Combining three TRS1D units together (additional units sold separately), one is able to test a Wye-Wye configuration with three phase ratio meters. When testing three phase ratio meters with the TRS1D, one uses the instrument's single phase or three phase excitation for testing. This is meant as a time saving feature, or to validate TTRU3 phase ratio meter models.

The TRS1D is primarily designed to be used in calibration facilities where accurate ratio transformation is required. In addition, the TRS1D is designed for rugged and easy use as a field ratio test kit. The connections are meant to handle large test clips. When ratio results of complex transformers are not as expected, the TRS1D provides the end user with field confirmation that the test instrument is working as intended and reporting ratio accurately.