Non-dispersive infrared fluid analyzer with compensation for absorptive and mechanical effects of ambient conditions专利检索-有限脉冲响应滤波器滤波器信号处理专利检索查询-专利查询网

Non-dispersive infrared fluid analyzer with compensation for absorptive and mechanical effects of ambient conditions

阅读：804发布：2022-01-05

专利汇可以提供Non-dispersive infrared fluid analyzer with compensation for absorptive and mechanical effects of ambient conditions专利检索，专利查询，专利分析的服务。并且Alternately chopped analytic and reference beams of infrared energy are passed through sample and reference fluids, respectively, and then sequentially through a first detector, a filter, and a second detector. Each detector is of the variable capacitor type responsive to pressure pulses, producing an output signal that is a function of the difference in the energies absorbed in the two beam paths. The first detector responds to absorption by the sample fluid due both to the component of interest and to an ambient condition (icluding the presence in the sample of an interferent having an absorption band overlapping that of the component in a spectral region where both are weakly absorbent). The second detector responds to absorption by the sample fluid due to the ambient condition alone. The filter limits the absorptive response of the second detector to an amount that will compensate for the similar response of the first detector to said ambient condition. The net output signal of the two detectors is a function of the difference of the individual outputs and responsive to component concentration. The two detectors are physically identical, and the signal output of the second detector may be adjusted to eliminate mechanical effects, such as vibration, due to other ambient conditions, without affecting the absorptive sensitivity of the instrument. A modification of more limited application, using a single beam, is also disclosed.，下面是Non-dispersive infrared fluid analyzer with compensation for absorptive and mechanical effects of ambient conditions专利的具体信息内容。

权利要求

1. In an infrared analyzer for measuring a component in a sample fluid mixture in the presence of an interferent having an absorption band overlapping that of the component, the combination including means for emitting beams of infrared energy along two beam paths, one an analytic beam and the other a reference beam, means for alternately interrupting said beams, a sample cell containing the sample fluid to be analyzed in the path of the analytic beam, a reference cell containing a reference fluid in the path of the reference beam, two infrared absorptive detectors of substantially identical physical structure and orientation in optical series relation to each other, each detector having two inner-connected absorption chambers respectively positioned in the two paths and being adapted to produce an output signal as a function of the difference in the energies absorbed in the two chambers, the chambers of the first detector containing a substance absorbing infrared energy in the same spectral region as the component in the sample cell, said region being one in which both the component and the interferent are weakly absorptive, and giving a first electrical signal response to variations of both the component and the interferent, the chambers of the second detector containing a substance absorptive in an adjacent spectral region where the sample fluid is absorptive due to the presence of the interferent alone and giving a second electrical signal responsive to variations in the interferent, attenuating means interposed in the optical paths of both beams between the two detectors for equally attenuating the energy in each of said beams to limit the signal response of the second detector to an amount that compensates for so much of the signal response of the first detector as is due to the presence of the interferent in the fluid sample, first and second amplifying means for amplifying the signal output of the first and second detectors respectively, means for independently adjusting the gain of each of said amplifying means, and differential amplifying means for producing a net output signal as a function of the difference in the amplified signals from the detectors.

2. Apparatus according to claim 1, in which each detector includes a separate condenser microphone having a diaphragm side and stator side and in which pressure pulses produced by energy absorption in the detector are applied to the same side of each microphone.

3. Apparatus according to claim 2, in which the attenuating means includes filter means adapted to contain a substance absorptive in said adjacent spectral region.

4. Apparatus according to claim 2, in which the absorptive substance in the chambers of the two detectors is of the same composition as the component, the amount of said substance in the first detector in the optical path of the analytic beam being greater than that in the sample cell but substantially less than that in the second detector in the optical path of the same beam.

5. Apparatus according to claim 4, in which the absorptive substance in the filter means is the same composition as the component.

6. Apparatus according to claim 5, in which the component is carbon monoxide and the interferent is water vapor.

7. Apparatus according to claim 1, in which the attenuating means between the two detectors includes filter means for limiting the infrared energy in the beams entering the second detector to a spectral region adjacent to but spaced from the spectral region in which infrared energy is absorbed in the first detector.

8. The method of adjusting an infrared analyzer having a source of infrared energy producing two beams, means for alternately modulating the two beams and means for optically Attenuating at least one of them, a sample cell in one beam path for holding a sample fluid containing a component of interest and an interferent, a reference cell containing a reference fluid in the other beam path, a first detector unit and a filter unit and a second detector unit in optical series relation and each provided with two chambers for holding a mixture of absorbing and non-absorbing fluids in the beam paths, all of the foregoing elements except the filter unit constituting the optical system of the apparatus, the detectors having pressure responsive means connected to an electric circuit that includes first amplifying means connected to the first detector unit and second amplifying means connected to the second detector unit and differential amplifying means for amplifying the difference between the amplified outputs of the detectors to produce a net output signal, said method including the following steps: (1) with the second detector receiving no infrared energy from the source, (a) attenuating one of the beams until the net output signal is zero in the absence of an absorbing fluid in the sample cell, and (b) with a known concentration of the component in a mixture of the component and a non-absorbing fluid in the sample cell, adjusting the gain of the first amplifying means until the net output signal is at a predetermined level corresponding to said component concentration, and (c) with a non-absorbing fluid in the sample cell and with said optical system subjected to vibration, adjusting the gain of the second amplifying means until the net output signal is zero; and (2) with both detectors receiving infrared energy from said source and with a mixture of the interferent and a non-absorbing fluid in the sample cell, adjusting the concentration of the absorbing fluid in the filter unit until the net output signal is zero.

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Non-dispersive infrared fluid analyzer with compensation for absorptive and mechanical effects of ambient conditions

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