A Wien filter electron spectrometer has been added to a VG Microscopes, Ltd. HB501 STEM to improve the energy resolution and accuracy of energy loss analysis combined with a high spatial resolution. An energy resolution of 130 mev is obtained with a 2 mR collection angle at the specimen. The 0. 28 ev wide field emission energy profile therefore dominates the energy resolution for the device. The energy axis is automatically calibrated by the electrostatic method of scanning, yielding an accuracy and stability of 30 mev. A preliminary energy resolution of 0. 5 ev is demonstrated for 20 mR full collection angles at the specimen. Results of experiments suggest that, even with a 0. 3 ev energy resolution, interband losses below 1. 5 ev will be hard to observe due to the long exponentially decaying field emission profile. Deconvolution procedures will probably be necessary as a result.