Wide range ultrasonic spirometer and its calculation method

Abstract

The invention discloses a wide-range ultrasonic pulmonary function instrument and a calculation method thereof. The wide-range ultrasonic pulmonary function instrument is provided with a blowpipe, an upstream ultrasonic transducer and a downstream ultrasonic transducer, wherein the upstream ultrasonic transducer and the downstream ultrasonic transducer are arranged on the wall of the blowpipe. An inclination angle is formed between the connection line of the upstream ultrasonic transducer and the downstream ultrasonic transducer and a channel wall. The upstream ultrasonic transducer is connected with a first filter circuit and a first isolating and driving circuit, and the downstream ultrasonic transducer is connected with a second filter circuit and a second isolating and driving circuit. The first filter circuit and the second filter circuit are connected with a channel selector, a programmable gain circuit, a voltage comparator and a GP22. The GP22 is in communication connection with a micro controller in a serial mode. The micro controller controls the channel selector, the programmable gain circuit and the voltage comparator. According to the calculation method, the difference, calculated last time, of time when the upstream ultrasonic transducer and the downstream ultrasonic transducer receive emission signals from each other is used for controlling the amplification factor of a programmable amplifier and the threshold value of the voltage comparator, so that accurate wide-range measurement is achieved. Compared with the prior art, bi-directional flow can be measured, zero pressure loss is achieved, the range is wide, and temperature compensation and pressure compensation are not needed.

Description

technical field [0001] The invention belongs to the technical field of medical detection, and in particular relates to a wide-range ultrasonic lung function instrument for measuring human lung function by using ultrasonic waves and a calculation method thereof. Background technique [0002] At present, the scheme of ultrasonic spirometer is based on the design method of industrial ultrasonic gas flowmeter. Two small ultrasonic sensors are installed in the upstream and downstream of the blowpipe, and the relationship between the propagation time difference of ultrasonic waves in forward flow and reverse flow and the gas flow rate is used to measure the instantaneous Flow rate and obtain various pulmonary function indicators through certain corresponding relations. However, since the ultrasonic spirometer is applied with a blowpipe with a very small diameter (the inner diameter is generally about 20mm), the gas flow rate is very high under the same flow rate, causing the ultra...

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Problems solved by technology

Due to the relatively low transmission efficiency of ultrasound in gas, the signal attenuation is relatively large, and the frequency of ultrasound is high, the noise is large, and the signal-to-noise ratio is difficult to improve, and the diameter of the lung function instrument is very small, and it is difficult to improve the accuracy.

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