An instrumentation system measures the concentrations of three principal contaminants (nonvolatile residue, hydrocarbon vapor, and particle fallout) in real time. The system includes a computer running special-purpose application software that makes it possible to connect the system into a network (which can, in turn, be connected to the Internet) to enable both local and remote display and analysis of its readings. The system was developed for use in a Kennedy Space Center facility that was required to be maintained at a specified high degree of cleanliness for processing a spacecraft payload that was highly sensitive to contamination. The system is also adaptable to monitoring contamination in other facilities and is an example of an emerging generation of sophisticated instrumentation systems that communicate data with other equipment.
The system includes a total of six sensors attached to a purged cart. There are two sensors of each type, for measuring the three principal contaminants at two different locations. The sensors for determining the concentrations of hydro- carbon vapors are Fourier-transform infrared (FTIR) spectrometers that measure the absorbance spectra of gases in internal gas cells in the wavelength range of 2.5 to 25 μm. The sensors for determining the concentrations of nonvolatile residues are surface-acoustic-wave devices, the resonance frequencies of which depend upon the amounts of material deposited on them. The sensors for monitoring particle fallout are small scatterometers.