Analysis can be done directly on samples or the analyser can process data acquired from a remote sensor.
For inline analysis, a sensor can be placed in a process vessel or stream of flowing material.
If the sample stream is not substantially modified by the analyser, it can be returned to the process.
Some methods of inline analysis are so simple, such as electrical conductivity or pH, the instruments are usually not even called analysers.
Chromatography such as ion chromatography or HPLC often tests the output stream continuously by measuring electrical conductivity, particularly cation or anion conductivity, refractive index, colorimetry or ultraviolet/visible absorbance at a certain wavelength.