Simulation tools are designed to represent subsets of the real world. To be effective, these tools must be experimentally validated with real world measurements. Sandia National Laboratories (SNL) and the National Renewable Energy Laboratory (NREL) have been tasked by the U.S. Department of Energy (USDOE) with the creation of a time-domain equation-of-motion simulator for the evaluation of wave energy converters, called WEC-Sim. A project for the experimental validation of WEC-Sim features has resulted in the development of custom instrumentation designed to characterize the forces affecting the power take-off (PTO) of the model wave energy converter (WEC). This paper describes the development of this instrument, a dynamometer, including the original project requirements, model specification, component choice, and capabilities. The inclusion of the dynamometer in the experimental model has a disruptive influence on the hydrodynamic operation. Prior to the laboratory experiments, the instrument is simulated using WEC-Sim output as a driving force to verify the dynamometer design in a virtual environment. The results of these simulations are reported here, demonstrating the process used to validate the design prior to physical implementation.