Abstract
Ultrasonic technology is widely used in the field of gas detection due to its advantages of low power consumption, high speed and strong adaptability to the environment. The current ultrasonic time-of-flight (TOF) measurement method has the large measurement error caused by ringing effect, and the phase detection method can only detect the phase change within 2π of a single cycle. These problems cannot meet the requirements of certain high concentration gas detection. This paper proposes a method of multi-frequency ultrasonic phase difference measurement to solve the problem that the phase difference across multiple cycles cannot be detected, hereby realizing full range gas concentration detection, and the continuous wave detection of this method also eliminates ringing effect in TOF. The phase difference within 2π of a single period is obtained by loading a single frequency driving signal on two channels, and the phase difference of low-frequency envelope of the modulated signal is obtained by loading multi-frequency modulated signals. The total cross-cycle phase difference can be obtained by combining the two results, and the measured gas concentration can be obtained by the relationship model between gas concentration and phase difference. The experimental results show that the average absolute error of 4% hydrogen concentration measurement is 0.12%, and the relative error of 99% hydrogen measurement is less than 5%. This method also provides a solution for extracting cross-cycle phase difference in other fields.
Highlights
Quantitative determination of specific gas components in a given background environment has important applications in many fields, such as detection of CO2 and N2O in environmental monitoring [1], [2], leakage detection of dangerous gas H2S and CL2 [3], [4], natural gas detection in production field [5], [6]
A dual-channel multi-frequency driving method is proposed to extract the total inter-cycle phase difference of ultrasonic waves, which solves the problem that the ultrasonic phase difference cannot be detected when phase difference was greater than 2π, and a full range detection from low concentration to high concentration of gas is realized based on the phase difference technology
This paper introduces a method of multi-frequency ultrasonic to achieve the detection of cross-cycle phase difference, which solves the detection problem of various gas concentrations
Summary
Quantitative determination of specific gas components in a given background environment has important applications in many fields, such as detection of CO2 and N2O in environmental monitoring [1], [2], leakage detection of dangerous gas H2S and CL2 [3], [4], natural gas detection in production field [5], [6]. Compared with TOF, the phase measurement method has the advantages of higher detection accuracy and lower power consumption, and has been widely used in other fields, such as temperature measurement, distance measurement, wind speed measurement, displacement measurement, and so on [29], [30] The principle of this method is to measure the phase difference between the signals received by ultrasonic and a fixed signal to reflect the change of sound speed. 2. For the first time, a dual-channel multi-frequency driving method is proposed to extract the total inter-cycle phase difference of ultrasonic waves, which solves the problem that the ultrasonic phase difference cannot be detected when phase difference was greater than 2π , and a full range detection from low concentration to high concentration of gas is realized based on the phase difference technology. The power consumption is lower than other gas detection methods
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