These are called energy dispersive instruments. Energy dispersive XRF instruments do not require a goniometer, and are thus of a much simpler mechanical design and are consequently less expensive.
In several cases, WDS systems offer the analyst an alternative to ICP or atomic absorption spectrometers, without the sample preparation complexity and particle size limitations commonly encountered with emission-type spectrometers.
Energy dispersive systems are identified primarily by their relatively simple optical path and unlike optical spectrometers, do not rely on diffraction. The most popular systems are bench top systems. In this case, their ultimate performance is largely determined by the quality of the X-ray source and the detector.