JPH0623736B2 - Ultrasonic densitometer - Google Patents

Description

The present invention relates to an ultrasonic densitometer for measuring the concentration of turbid substances contained in a sample solution.

<Prior Art> An ultrasonic densitometer is a means for measuring the concentration of turbid substances such as cement and sludge contained in a sample solution. This ultrasonic densitometer includes a concentration detector in which a transmitter for transmitting ultrasonic waves into a sample solution and a receiver for receiving ultrasonic waves propagated in the sample solution are arranged to face each other with a predetermined distance. Then, when ultrasonic waves are radiated into the sample solution from the transmitter of the concentration detector, the radiated ultrasonic waves are attenuated according to the concentration of the turbid substance in the sample solution. When the ultrasonic wave propagating in the sample liquid is received by the receiver, a received signal corresponding to the received ultrasonic wave is output from the receiver, so that the signal intensity of this received signal is measured. Thereby, the concentration of the turbid substance in the sample solution is measured.

<Problems to be Solved by the Invention> When the temperature of the sample liquid changes, the sound velocity of the ultrasonic wave propagating in the sample liquid changes accordingly. Then, this change in sound velocity causes a change in the attenuation coefficient of ultrasonic waves. As a result, the temperature change appears as an error in the measured concentration of the sample solution.

In the conventional ultrasonic densitometer, no means for compensating for the influence of the temperature change is provided, so that there is a problem that the influence of the sound velocity of the ultrasonic wave due to the temperature change cannot be avoided.

The present invention has been made in view of the above problems, and an object of the present invention is to enable effective compensation of the influence of temperature when measuring the concentration of a sample liquid.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention inputs the excitation driving oscillation transmission signal applied to the transmission element and the reception signal output from the reception element in common, It is characterized by including a temperature correction circuit for outputting a temperature correction signal having a pulse width corresponding to the propagation time of an ultrasonic wave propagating in the sample liquid.

<Operation> The propagation time of the ultrasonic wave in the sample solution is converted into a temperature correction signal having a pulse width corresponding to the propagation time by the temperature compensation circuit. Therefore, when the temperature of the sample liquid changes, the sound velocity of the ultrasonic wave propagating in the sample liquid also changes, but this change in the sound velocity results in a change in the pulse width. Therefore, the received signal corresponding to the concentration of the sample solution output from the receiver can be corrected based on the temperature correction signal obtained by the temperature correction circuit.

<Examples> Hereinafter, the present invention will be described in detail based on Examples shown in the drawings.

FIG. 1 is a block diagram of an ultrasonic densitometer showing an embodiment of the present invention. In the figure, reference numeral 1 indicates an ultrasonic densitometer,
Reference numeral 2 is a concentration detection unit, and 4 is a sample liquid containing turbid substances such as cement and sludge. The concentration detection unit 2 includes a container 6 that stores the sample solution 4, and a transmitter 8 that transmits ultrasonic waves into the sample solution 4 and a receiver 10 that receives the ultrasonic waves propagated in the sample solution 4. It is configured to be opposed to each other with a predetermined distance maintained. Reference numeral 12 is an oscillator that outputs a transmission signal for driving the oscillator 8; 14 is an on / off switch; 16 is an on / off switch.
A switching pulse generator that generates a switching pulse for operating the off switch 14 and a first amplifier 18 that amplifies a transmission signal output from the oscillator 12. Further, 20 is a second amplifier that amplifies the received signal output corresponding to the intensity of the ultrasonic wave received from the receiver 10, 22 is a rectifier that rectifies the received signal of the second amplifier 20, and 24 is a rectifier 22. DC that linearly corresponds to the concentration of the sample liquid 4 of the rectified received signal
It is an antilogarithmic amplifier that converts a voltage concentration signal and amplifies and outputs it.

Further, in the ultrasonic densitometer 1 of this embodiment, an ultrasonic wave driving signal applied to the oscillator 8 and a received signal output from the receiver 10 are commonly input to propagate the ultrasonic wave in the sample solution. A temperature correction circuit 26 that outputs a temperature correction signal having a pulse width corresponding to the propagation time of a sound wave is provided. The temperature correction circuit 26 receives a signal for excitation drive applied to the oscillator 8 and generates a trigger pulse, and a first trigger pulse generator 28, and receives a reception signal output from the receiver 10 to generate a trigger pulse. A second trigger pulse generator 30 to be generated, first and second trigger pulse generators 28,
R to input the trigger pulse output from each 30
S flip-flop 32 and RS flip-flop 32
Pulse width / voltage converter 34 for converting the pulse width of the output signal of the above into a DC voltage corresponding thereto, and the DC voltage output from this pulse width / voltage converter 34 are multiplied by a constant ratio coefficient to correct the temperature. It is composed of a multiplier for converting into a signal. Further, 38 is an adder for adding the temperature correction signal output from the multiplication circuit 36 of the temperature correction circuit 26 to the concentration signal output from the antilogarithmic amplifier 24, and 40 is the temperature-corrected DC output from the adder 38. It is a voltage / current converter that converts a voltage value into a current value.

The operation of each part when the concentration of the turbid substance in the sample liquid 4 is measured by applying the ultrasonic densitometer 1 will be described with reference to the time chart shown in FIG.

First, from the switching pulse generator 16 to the on / off switch 1
4 is given a switching pulse, the on / off switch 1
As shown in FIG. 2 (a), 4 maintains the ON state only during the period T1 in which the switching pulse is applied. Moreover, the time interval T2 from one ON period of the ON / OFF switch 14 to the next ON period is set to a predetermined value T2 in consideration of the ultrasonic wave transmission / reception period in the concentration detection unit 2. Therefore, the on / off switch 14 is set to the set time interval T
The ON / OFF operation is intermittently repeated with 2. Then, when the on / off switch 14 is in the on state, the oscillation signal output from the oscillator 12 is transmitted via the on / off switch 14 to the first amplifier 18 as shown in FIG.
The oscillator 8 and the first trigger pulse generator 2 after being amplified by
Join 8 and. When a transmission signal is applied to the oscillator 8, the oscillator 8 is excited and driven by this, and emits ultrasonic waves into the sample solution 4. The ultrasonic waves radiated into the sample solution 4 are attenuated according to the concentration of the turbid substance in the sample solution 4. In this way, the ultrasonic wave propagated in the sample liquid 4 is received by the receiver 1 after a certain time T3.
Received with 0. When receiving the ultrasonic wave, the receiver 10 outputs a reception signal corresponding to the intensity of the received ultrasonic wave, as shown in FIG. In this received signal, the ultrasonic wave radiated from the transmitter 8 is directly received by the receiver 10 and becomes a reflected wave, and after one round trip between the oscillator 8 and the receiver 10, or after several round trips. What is received by the receiver 10 appears.

The reception signal output from the receiver 10 is input to the second amplifier 20 and the second trigger pulse generator 30, respectively.
The second amplifier 20 amplifies the input reception signal and supplies it to the rectifier 22 in the next stage. The rectifier 22 rectifies the input reception signal into a DC voltage. The rectified received signal is then provided to the antilogarithmic amplifier 24. The inverse logarithmic amplifier 24 converts the received signal rectified by the rectifier 22 into a DC voltage concentration signal linearly corresponding to the concentration of the sample liquid 4.

On the other hand, when an oscillation signal for driving the oscillator 8 is applied to the first trigger pulse generator 28, the first trigger pulse generator 2
8 generates a trigger pulse, which is applied to the set input terminal of the RS flip-flop 32. As a result, the RS flip-flop 32 is set and a high level signal is output. Further, when the reception signal output from the receiver 10 is applied to the second trigger pulse generator 30, the second trigger pulse generator 30 generates a trigger pulse, and this trigger pulse is applied to the reset input terminal of the RS flip-flop 32. Given. As a result, the RS flip-flop 32 is reset and the high-level signal output is inverted to the low level. Therefore, as shown in FIG. 2D, the RS flip-flop 32 outputs a signal having a pulse width corresponding to the propagation time T3 of the ultrasonic wave propagating in the sample liquid 4. That is, since the pulse width of the signal output from the RS flip-flop 32 is a function of temperature, when the temperature of the sample liquid 4 changes, the temperature change appears as a change in pulse width.
The output signal of the RS flip-flop 32 is converted into a DC voltage corresponding to the pulse width by the pulse width / voltage converter 34 in the next stage. The signal converted into the DC voltage by the pulse width / voltage converter 34 is further input to the multiplier 36. The multiplier 36 multiplies the signal output of the pulse width / voltage converter 34 by a constant ratio coefficient and converts the signal output into a temperature correction signal. Then, in the next stage adder 38, the antilogarithmic amplifier 24
The temperature correction signal output from the multiplication circuit 36 is added to the concentration signal output from the output circuit, and the temperature of the concentration signal is corrected. The temperature-corrected signal output from the adder 38 is converted by the voltage / current converter 40 into a corresponding current value.

In addition to the above embodiment, for example, as shown in FIG.
The on / off switch 44 is provided between the second amplifier 20, the second trigger pulse generator 30 and the receiver 10, and the switching pulse generator 16 is provided with the delay circuit 42, so that the reception signal output from the receiver 10 is provided. It is also possible to configure so as to remove the one based on the reflected wave in the.

<Effects of the Invention> As described above, according to the present invention, the propagation time of the ultrasonic wave in the sample solution is converted into the temperature correction signal having the pulse width corresponding to the propagation time by the temperature compensation circuit, and the temperature correction signal is converted into the temperature correction signal. Based on this, the received signal output from the receiver is corrected. Therefore, it is possible to effectively compensate for the influence of the change in the propagation velocity of the ultrasonic wave due to the temperature, even if the temperature sensor is not provided. Therefore, the concentration of the turbid substance in the sample liquid can be measured more accurately than in the conventional case.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic densitometer showing an embodiment of the present invention, FIG. 2 is a time chart of output signals of the ultrasonic densitometer of FIG. 1, and FIG. 3 is an application example of the present invention. It is a block diagram of an ultrasonic densitometer. 1 ... Ultrasonic densitometer, 2 ... Concentration detector, 4 ... Sample solution, 8 ... Oscillator, 10 ... Receiver, 26 ... Temperature correction circuit.

Claims (1)

[Claims] 1. An ultrasonic wave concentration comprising a concentration detector in which a transmitter for transmitting an ultrasonic wave into a sample solution and a receiver for receiving an ultrasonic wave propagated in the sample solution are opposed to each other with a predetermined distance therebetween. In the meter, a pulse width corresponding to a propagation time of an ultrasonic wave propagating in the sample liquid by commonly inputting an excitation driving oscillation signal applied to the oscillator and a reception signal output from the receiver is provided. An ultrasonic densitometer, comprising a temperature correction circuit that outputs a temperature correction signal.