Method of monitoring pressure of a gas species and apparatus to do so

Abstract

A method of monitoring pressure of a gas species up to at most a predetermined maximum pressure value is disclosed. The method includes exposing the gas species to transmission of laser light, periodically modulating the wavelength of the laser light over a wavelength band including at least one absorption line of the gas species, optoelectrically converting the transmitted laser light, thereby generating an electric output signal, performing at least one of first filtering the electric output signal with a filter characteristic having a lower cut-off frequency not lower than a transition frequency and of second filtering the electric output signal with a bandpass filter characteristic having an upper cut-off frequency not higher than the transition frequency and a lower cut-off frequency above the modulation frequency of the periodic wavelength modulation. The output of at least one of the filterings is evaluated as a pressure indicative signal.

1 . A method for manufacturing closed, filled containers transparent to laser light, the pressure of a gas species therein being monitored, comprising:
 manufacturing a closed, filled container transparent to said laser light;   exposing said container to transmission of laser light;   providing said laser light with wavelengths spread over a wavelength band including at least one absorption line of said gas species;   optoelectrically converting said transmitted laser light, thereby generating an electric output signal;   performing upon said electric signal a filtering comprising first filtering and second filtering;   performing said first filtering so that the output signal of said first filtering varies with a first characteristic as a function of said pressure;   performing said second filtering so that the output signal of said second filtering varies with a second characteristic as a function of said pressure;   said first characteristic being different from said second characteristic;   evaluating from signals dependent on the output signals of said first and second filtering said pressure indicative signal.   
   
   
       2 . The method of  claim 1 , further comprising performing at least one of said first and of said second filtering as band pass filtering. 
   
   
       3 . The method of  claim 1 , further comprising performing said first and second filtering in non-overlapping frequency areas of the spectrum of said electric output signal. 
   
   
       4 . The method of  claim 1 , further comprising performing said first and said second filtering as band pass filtering. 
   
   
       5 . The method of  claim 1 , further comprising performing said first and second filtering in first and second frequency ranges respectively, the energy of said electric output signal having a first energy vs. pressure characteristic in said first frequency range and a second energy vs. pressure characteristic in said second frequency range, said first and second energy characteristics being different from each other. 
   
   
       6 . The method of  claim 1 , wherein said providing said laser light with wavelengths spread over said wavelength band is performed by periodically modulating the wavelength of a laser. 
   
   
       7 . The method of  claim 1 , wherein said first filtering and second filtering are performed in parallel. 
   
   
       8 . A method for monitoring pressure of a gas species up to at most a predetermined maximum pressure value comprising:
 exposing said gas species to transmission of laser light;   providing said laser light with wavelengths spread over a wavelength band including at least one absorption line of said gas species;   optoelectrically converting said transmitted laser light, thereby generating an electric output signal;   performing upon said electric signal a filtering comprising first filtering and second filtering;   performing said first filtering so that the output signal of said first filtering varies with a first characteristic as a function of said pressure;   performing said second filtering so that the output signal of said second filtering varies with a second characteristic as a function of said pressure;   said first characteristic being different from said second characteristic;   evaluating from signals dependent on the output signals of said first and second filtering said pressure indicative signal   
   
   
       9 . The method of  claim 8 , further comprising performing at least one of said first and of said second filtering as band pass filtering. 
   
   
       10 . The method of  claim 8 , further comprising performing said first and second filtering in non-overlapping frequency areas of the spectrum of said electric output signal. 
   
   
       11 . The method of  claim 8 , further comprising performing said first and said second filtering as band pass filtering. 
   
   
       12 . The method of  claim 8 , further comprising performing said first and second filtering in first and second frequency ranges respectively, the energy of said electric output signal having a first energy vs. pressure characteristic in said first frequency range and a second energy vs. pressure characteristic in said second frequency range, said first and second energy characteristics being different from each other. 
   
   
       13 . The method of  claim 8 , wherein said providing said laser light with wavelengths spread over said wavelength band is performed by periodically modulating the wavelength of a laser. 
   
   
       14 . The method of  claim 8 , wherein said first filtering and second filtering are performed in parallel.