Three different types of specialized spectrometers have been implemented. These sensors are well suited for gas detection or other industrial applications where long-term stability is a key requirement. These sensors are based on tunable diffractive filters that were developed in the past and that we have now adapted to fit into the presented spectrometers, each of them developed to perform a dedicated measurement. The diffractive filters share the common feature that a single surface hologram integrates the functions of lenses, beam splitters and spectral filters. In order to perform a compensated measurement, it is possible to switch between several filter functions, which can be done without the need for complicated or precise mechanical control. These features make it possible for the spectrometers to be made robust against long-term drift, which eliminates the need for frequent recalibration and maintenance. In addition, the simplicity of the sensor assembly makes the sensors well suited for a wide range of applications; the requirement is either a low production cost or robustness to harsh industrial environment. The sensors are or have been industrialized, with application mainly for gas spectroscopy. Results in terms of sensitivity and long-term drift were obtained in the field and are presented.