In recent years, the quadrupole sensor has increasingly been used in new applications far away from vacuum technology, often with the demand for quantitative results. The use of simple, low-cost RGA's for quantitative measurements often yields disappointing results which spoil the reputation of the principle as a quantitative method. Typical classes of quantitative measurements will be listed and correlated with typical specifications of the quadrupole. It will be shown that many practically important quantitative measurements only require a stable instrument. For quantitative analysis of mixtures with strongly varying components a good linearity is additionally required. As a practical example for the quadrupole as a process gas analyzer the PGA 100 from Leybold-Heraeus will be taken. It will be shown that, paying attention to its limits, even a small quadrupole instrument can have the stability and linearity required for reliable quantitative measurements.
