Fluorescent gas analyzer

Claim 2

Apparatus for measuring the concentration of a fluorescent constituent in a gaseous sample, said apparatus comprising: a sample chamber provided with means for introducing a sample into the chamber; a gaseous discharge flash-tube optically coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, saiD flashtube being provided with energy storage means which can provide to said flashtube a momentary current pulse of high intensity and supply means for recharging said energy storage means between flashes; timing means for repetitively flashing said tube at intervals which are relatively long as compared with the flash duration; a photodetector optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photodetector being provided with filter means for confining detected energy to a second predetermined wavelength region; circuit means for integrating said signal over the duration of each flash to generate a sample signal responsive to the fluorescent energy given off by the sample during the flash; means for resetting said integrating means between successive flashes; and means for sampling said sample signal substantially at the end of each flash and before resetting for generating a continuous output signal which substantially follows the successive sample signal values.

Claim 3

Apparatus as set forth in claim 1 wherein said flash-tube is a Xenon flash-tube through which an energy storage capacitor is repetitively discharged.

Claim 4

Apparatus as set forth in claim 1 wherein said timing means is a free-running multivibrator.

Claim 5

Apparatus as set forth in claim 1 wherein said photo-detector is a photo-multiplier providing a current which is essentially proportional to the detected fluorescence and wherein said circuit means includes a capacitor which, on a short-term basis, integrates said current.

Claim 6

Apparatus as set forth in claim 4 wherein said capacitor is shunted by a resistor for substantially discharging said capacitor between flashes.

Claim 7

Apparatus as set forth in claim 5 including means for adjusting the nominal d.c. level of said integrated signal.

Claim 8

Apparatus for measuring the concentration of a fluorescent constituent in a gaseous sample, said apparatus comprising: a sample chamber provided with means for drawing a sample into the chamber; a gaseous discharge flash-tube optically coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with filter means for confining said energy to a first wavelength region; timing means for repetitively flashing said tube; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a second predetermined wavelength region; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; and a sample and hold circuit for sampling the voltage on said capacitor substantially at the end of each flash and for generating a continuous output signal which substantially follows the successive sample voltage values.

Claim 9

Apparatus for measuring the concentration of a fluorescent constituent in a gaseous sample, said apparatus comprising: a sample chamber provided with means for drawing a sample into the chamber; a gaseous discharge flash-tube optically coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with filter means for confining said energy to a first wavelength region; timing means for repetitively flashing said tube; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a second predetermined wavelength region; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; and a sample and hold circuit for sampling the voltage on said capacitor substantially at the end of each flash and for generating a continuous output signal which substantially follows the successive sample voltage values.

Claim 10

Apparatus as set forth in claim 7 wherein said sample chamber includes a light trap opposite said flash-tube.

Claim 11

Apparatus as set forth in claim 7 wherein said capacitor is shunted by a resistor for substantially discharging said capacitor between successive flashes and wherein said circuit means includes means for adjusting the d.c. level of the integrated signal.

Claim 12

Apparatus for measuring the concentration of a fluorescent constituent in a gaseous sample, said apparatus comprising: a sample chamber provided with means for drawing a sample into the chamber; a Xenon flash-tube opticaLly coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with filter means for confining said energy to a first wavelength region; timing means for repetitively flashing said tube, said means including a free-running multivibrator generating relatively short pulses at relatively long intervals, the flash-tube being triggered at the start of each short pulse; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a second predetermined wavelength region; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; a sample and hold circuit for sampling the voltage on said capacitor; a one-shot multivibrator for generating short pulses which are initiated at the end of each pulse generated by said free-running multivibrator; and means for causing said sample and hold circuit to sample during the pulses generated by said one-shot multivibrator, whereby said sample and hold circuit generates a continuous output signal which substantially follows the successive sample voltage values.

Claim 13

Apparatus for measuring the concentration of a fluorescent constituent in a gaseous sample, said apparatus comprising: a sample chamber provided with means for drawing a sample into the chamber; a Xenon flash-tube opticaLly coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with filter means for confining said energy to a first wavelength region; timing means for repetitively flashing said tube, said means including a free-running multivibrator generating relatively short pulses at relatively long intervals, the flash-tube being triggered at the start of each short pulse; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a second predetermined wavelength region; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; a sample and hold circuit for sampling the voltage on said capacitor; a one-shot multivibrator for generating short pulses which are initiated at the end of each pulse generated by said free-running multivibrator; and means for causing said sample and hold circuit to sample during the pulses generated by said one-shot multivibrator, whereby said sample and hold circuit generates a continuous output signal which substantially follows the successive sample voltage values.

Claim 14

Apparatus for measuring the concentration of SO2 in a gaseous sample, said apparatus comprising: a sample chamber provided with means for pumping a sample gas through the chamber; a Xenon flash-tube optically coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with a bandpass filter means for confining said energy to a wavelength region around 2,200A, said sample chamber being provided with a light trap opposite said flash-tube; timing means for repetitively flashing said tube at a preselected power level; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a wavelength region around 3,600A; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; a sample and hold circuit for sampling the voltage on said capacitor; and means for initiating a sampling of the capacitor voltage a preselected, relatively short interval after each flash and for terminating the sampling a preselected, relatively short interval after initiation and before said capacitor is significantly discharged thereby to generate a continuing output signal which substantially follows the successive sample voltage values.

Claim 15

Apparatus for measuring the concentration of SO2 in a gaseous sample, said apparatus comprising: a sample chamber provided with means for pumping a sample gas through the chamber; a Xenon flash-tube optically coupled to said chamber along a first axis for illuminating a sample therein with radiant energy, said flash-tube being provided with a bandpass filter means for confining said energy to a wavelength region around 2,200A, said sample chamber being provided with a light trap opposite said flash-tube; timing means for repetitively flashing said tube at a preselected power level; a photo-multiplier tube optically coupled to said chamber along an axis transverse to said first axis for detecting fluorescent radiant energy given off by a sample in said chamber and for generating an electric current signal responsive to said detected energy, said photo-multiplier tube being provided with filter means for confining detected energy to a wavelength region around 3,600A; circuit means including a capacitor for integrating said current signal over the duration of each flash to generate a sample voltage responsive to the fluorescent energy given off by the sample during each flash and for discharging said capacitor between flashes; a sample and hold circuit for sampling the voltage on said capacitor; and means for initiating a sampling of the capacitor voltage a preselected, relatively short interval after each flash and for terminating the sampling a preselected, relatively short interval after initiation and before said capacitor is significantly discharged thereby to generate a continuing output signal which substantially follows the successive sample voltage values.