Shimadzu Corporation

Shimadzu Co.

Fumiaki Otera

Rui Kato

Hideaki Katsu

Modulation amplitude used for frequency modulation of laser light is set to a1 (&#x3c;a2) (S1), and laser light is irradiated to a sample state in that state. When moisture concentration is calculated based on secondary harmonic synchronous detection signal that is obtained by synchronous detection of detection signal from transmitted light, the effects of interfering moisture in the optical chamber is ignored, and moisture concentration of the gas to be measured in the sample cell is obtained (S2). If, for example, a high vacuum is created inside the sample cell and the concentration becomes less than the detectable limit ('YES' in S3), the modulation amplitude is switched to a larger amount a2 (S4). By so doing, the detection sensitivity to interfering moisture in atmosphere at atmospheric pressure is increased, and the concentration of interfering moisture is calculated based on the secondary harmonic synchronous detection signal (S5).

Device for measuring moisture in a gas

A gas analyzer is provided, capable of measuring specific gas amount information within a measurement target gas in which pressure varies greatly. The gas analyzer includes a calculation member for calculating specific gas amount information of the nth cycle, a gas pressure change amount calculation unit for calculating an amount of gas pressure change at each time, and a correction signal creation member for generating a time changing, corrected light intensity at each wavelength &#x3bd;, by performing a fitting process using the time-changing intensity over a long time period in a time zone in which the amount of gas pressure change is small but using the time-changing intensity over a short time period in a time zone in which the amount of gas pressure change is large. The calculation member generates a light intensity change of the measurement light in the predetermined wavelength range of &#x3bd;1 to &#x3bd;2 of the nth cycle by using the time changing, corrected light intensity at each wavelength &#x3bd;, and calculates the specified gas amount information for the nth cycle.

Gas analyzer

If the specific gas concentration is relatively high, controller sets 0 as the modulation amplitude in a modulation amplitude controlling voltage generator for frequency modulation of laser light, controls a switching unit to select the output of a second ADC, and causes a computation unit to compute according to the direct absorption detection method to calculate the water molecule volume concentration. If the specific gas concentration is relatively low, the modulation amplitude is set to A, not 0, controls switching unit to select the output of a first ADC, which digitizes a synchronized detection signal, and causes the computation unit to compute according to the harmonic synchronous detection method to calculate the water molecule volume concentration. The concentration calculated using either of the methods is compared against a threshold value, and if decided that an accurate result cannot be obtained, the method is switched as the measurements are continuously executed.

Gas analysis device

A gas analyzer is capable of detecting abnormality of a measurement environment without using either or both of a pressure sensor and a gas temperature sensor. The gas analyzer creates absorption spectra from transmitted light intensity of laser beams applied to gas for measuring the amount of spread W and compares the amount of spread against a threshold D. The amount of spread of the absorption spectra does not depend on pressure if the pressure of the gas to be measured falls within a high-vacuum region, and monotonously increases with increased pressure if the pressure of the gas to be measured is higher than the high-vacuum region. Thus, if W&#x3e;D, it is determined that the measurement environment does not form a high-vacuum region and abnormality is transmitted to the outside. In all other cases, the measurement environment is deemed to form a high-vacuum region, and partial pressure is calculated.

A gas analyzer includes: a first signal processing section for synchronously detecting a light detection signal at a frequency being an integral multiple of a modulation frequency fa of a laser light, to detect a harmonic signal intensity Signal(&#x3bd;) by a harmonic synchronous detection method; a second signal processing section for capturing a light detection signal and cutting off a frequency component not smaller than the frequency fa to detect a light intensity signal I(&#x3bd;) at a specific light frequency absorbed by a component to be measured in a sample gas; and an operation section. The operation section includes a first operation means for calculating a density c of the component from the harmonic signal intensity Signal(&#x3bd;) and a reference light intensity signal I(&#x3bd;) and a second operation means for calculating the density c from the light intensity signal I(&#x3bd;) and the reference light intensity signal I(&#x3bd;).

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Kyoto, Japan

Fumiaki Otera