| 摘要 |
PURPOSE:To allow the heater to emit adequate thermions for obtaining sufficient signal to noise ratio and elongate the operating life of the heater by measuring a signal to noise ratio of analyzed value and controlling a current value of the heater for emitting thermions so that the said value becomes equal to the set value. CONSTITUTION:A valve 2 is switched to calibration gas 13 from the duct 1. The gas reservoir 13 is filled with a gas in such a concentration as equivalent to respiration gas and it is analyzed and the amount of ion proportional to the concentration is collected in the collector 11 to output a voltage. At this time, an output voltage of collector 12-3 for CO2 is applied to a bypass filter 14 and a low-pass-filter 15, a high-pass-filter 14 extracts only noise signal and it is applied to the amplitude detection circuit 16 and thereby an amplitude value can be obtained. A division circuit 17 calculates a signal to noise ratio, such value is applied to the comparator circuit 18 and is compared with a value of signal- to-noise setting circuit 19. Such output is applied to the control voltage generating circuit 20 and thereby an optimum current is supplied to the heater. Thereby, operating life of heater can be elongated and maintenance characteristic of apparatus can be improved. |
