A controller for operating a rod pumping unit includes a processor configured to operate the rod pumping unit at a pumping profile speed. The processor is further configured to compute a first downhole dynamometer card from surface measurements at the rod pumping unit. The processor is further configured to compute a second downhole dynamometer card from the surface measurements. The processor is further configured to validate at least one of the first downhole dynamometer card and the second downhole dynamometer card based on a rod pumping unit condition.