JPS58202829A - Ultrasonic wave doppler flowmeter - Google Patents

Abstract

PURPOSE:To obtain a highly accurate ultrasonic wave doppler flowmeter which is stable with respect to the fluctuation of a received signals, by imparting hysteresis to a zero crossing comparator, and changing the value in correspondence with the magnitude of a doppler shift signal that is inputted in the comparator. CONSTITUTION:An electric signal from a transmitting part 102 is converted into an ultrasonic wave by a transmitting element 104 and transmitted to fluid to be measured. The ultrasonic wave reflected by a scattering body 106 in the fluid is received by a receiving element 108 together with the transmitted wave. Only the signal including doppler shifted components is taken out through a high frequency amplifier 202 and an envelope detector 204. The signal is inputted in a zero crossing comparator 302 and a full wave rectifier 304 through a filter 206 and a low frequency amplifier 208. The full wave rectified signal becomes a reference signal for the comparator 302 through a mean detector 306 and a hysteresis controller 308. The doppler shift frequency from the comparator 302 is computed through a frequency/voltage converter 402 and a cross sectional area correcting part 404, and a flow rate output 5 is obtained highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic Doppler flowmeter that measures the flow rate of a fluid by measuring the Doppler knot frequency.

In conventional ultrasonic Doppler flowmeters, a comparator is generally provided within the signal processing means to discriminate between the Doppler knot frequency and the noise signal. At that time, the signal that should serve as the reference value of the comparator was set to a fixed value by dividing the voltage using positive and negative constant current positive metal voltage dividing resistors.

Therefore, when the received signal changes significantly and the input signal of the comparator changes accordingly, the M sound component cannot be effectively removed or a counting error occurs.

If one input word becomes more obscene than the reference value, the positive error, which can be predicted by the noise superimposed on the input signal, becomes significantly smaller. In some cases, the signal was hidden below the reference value and was not detected, resulting in a negative error.

In addition to the above-mentioned causes, such counting errors also occur due to deterioration of the characteristics of the transmitter/receiver and changes over time in the gain of high/low frequency amplification≦.

Akira Peyaku: L1. , It was done to eliminate all the entry points of Kami Tsukuda Hana Bei Soho, and it is stable for the above-mentioned various causes. The purpose is to provide a total of 1%.

, −′r′! - In order to achieve this, in the present invention, a cellocross comparator (hereinafter referred to as a comparator,...!) is given a hysteresis value of 7, and its value is changed to the magnitude of the error input to the comparator. 9
Be detailed.

An example of the present invention will be explained below with reference to the drawings.
411] shows its overall configuration.

Electricity No. 1 from the transmitter 102 is converted into three sound waves by the transmitter 104, and transmitted as a signal to the fluid to be measured. The sound detection body 106 reflected in the fluid is received by the receiver 108, and the sound detection device 2012 and the envelope detector 204 are connected to the tonoplane knot. Signal 77 including skin σ: injury is detected. This signal j is filtered by a filter 2061 to remove all noise components exclusive to the epidermis noise, and then amplified by the skin intensifier 208, and the input signal j of the cross comparator 302 is input to the input signal j: 'A m.

This input signal is directly input to the comparator 302.
and a signal input to the full-wave rectifier 304. The full-wave rectified signal is sent to an average value detector 30.
The reference signal of the comparator 302 is inputted to the hysteresis copy 14308 which compares the output signal of the comparator 302 with a diameter of 6, converts it to hysteresis, and then divides it by the resistors R, , R, to produce the reference signal of the comparator 302. becomes.

The Doppler 778 cycle inverse number 1fi calculated from the input signal by the above comparator is converted into DC signal yvcx-s by the frequency/voltage compensator 402. Since this DC voltage is proportional to the flow velocity, the cross-section 1Ki product correction unit 404 performs a routine to avoid excessive cross-section dipping, and the flow rate output 5 is obtained.

Next, the waveforms from a to e in FIG. 1 are shown in FIG. 2 with symbols a to e, respectively.

The received signal waveform includes the dock puller shift number which has been doubled by the interference 202, and has been negative wave by the time it is input to the comparator 302.
This will happen. c, d are the output shapes of the full-wave rectifier 304 and the output signal generator 306, e is the reference value (hysteresis) of the comparator that changes according to the input signal δ, and the relationship between g・mab and e. It is a composite waveform.

As shown in FIG. 2, when the input signal becomes smaller, the hysteresis becomes smaller accordingly, so that a slight measurement error τ does not occur. Also, when the input signal becomes weaker;
In this case, the hysteresis also becomes sharper, and the four tones M folded around zero are effectively removed.

As described above, according to the present invention, the hysteresis of the cellocross comparator with hysteresis always recedes to the level of the input signal. This is due to changes in the gain of the tube over time and changes in the degree of acoustic coupling between the conduit wall and the tube.
Even if the input signal changes dramatically, the ratio between the input signal and the hysteresis is always small, so it is difficult to count the Donplanft frequency with high accuracy and stability.

゛4-sided D-4J Brief explanation No. 11 is a diagram showing the overall configuration of an embodiment of the present invention.
The figure is a diagram showing the inverse shape of the signal f at each point in FIG.

102... Transmitter, 104... Transmitter, lo6...
・Saran books, etc., 108...Receiver, 2o2...High frequency 1. Broadband detector, 204... Envelope detector, 206...
Filter, 208...Low frequency amplifier, 3o2...
Cell cross comparator, 304...Full wave rectifier, 3
o6...Average value detector, 308...Hysteresis system @"S, 402...Frequency/voltage converter 404.
...Cross-sectional area, 5...Flow rate output.

Agent: Ben/author: Meihiro Takahashi Jθ6 t　2fig.

Claims (1)

[Scope of Claims] 1. - Transmitting means for transmitting ultrasonic waves at a foot frequency to a constant fluid to be subjected to the transmission, and ultrasonic receiving means for receiving reflected waves including a Doppler shift frequency by the fluid; producing means for detecting the Doppler shift frequency from the output of the receiving means; control signal generating means for receiving the output of the detecting means as an input signal and generating a control signal proportional to the magnitude of the input signal; and the control signal. a comparator which receives the input signal and compares the two signals, and a reference signal generating means which inputs the output of the comparator and the side leg signal generating means Deba and generates the reference signal. An ultrasonic Doppler flowmeter comprising a signal processing means and a signal processing means.