Definition of spectrometer. 1  1 : an instrument used for measuring wavelengths of light spectra. 2  2 : any of various analytical instruments in which an emission (as of particles or radiation) is dispersed according to some property (as mass or energy) of the emission and the amount of dispersion is measured nuclear magnetic resonance spectrometer.
1 bar is equal to 1000 millibars. Just like how there are 1000 millilitres in a litre, and 1000 milliseconds in a second. 1 millibar = 0.001 bars.
a metric unit of pressure equal to 100 pascals or 0.1 kilopascal (kPa). The hectopascal, used almost entirely in measurements of air pressure, is identical to the millibar (mb). The millibar has been used to measure air pressure for many years, but it is not an SI unit.