JPS6097247A - Continuous liquid-concentration measuring device - Google Patents

Abstract

PURPOSE:To measure the concentration of liquid accurately in a short time, by applying a pulse voltage across electrodes. CONSTITUTION:In a pulse-voltage applying means 1, a switching circuit 12 is turned On by a square wave formed by a one-shot pulse generating circuit 15. A square pulse voltage (e) having a short pulse width is applied across A and C of a liquid-concentration detecting means 2. In the part between B and C of electrodes (P) of the liquid-concentration means 2, which is immersed in the liquid, impedance, which is determined by the liquid concentration, is present. When a divided voltage e' between B and C of the square pulse voltage (e) is measured, the liquid concentration can be detected. The potential difference e' between the electrodes is compared with a preset reference voltage 18 in a measuring means 3, operation is performed, and the measured data is outputted to an output circuit 20. In this constitution, disturbance in electrode potential due to fluidness is not present even though the liquid is flowing. Gas is not yielded and polarization does not occur at the time of measurement.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a fluid concentration measuring device.

<Prior art> Conventionally, in order to measure and monitor the concentration of liquid, quantitative analysis,
Instruments such as hydrogen ion concentration measurement, specific gravity measurement, and electrical conductivity measurement have been used.

Quantitative analysis requires preparation of the sample to be measured, and continuous measurement requires complicated and expensive equipment. Hydrogen ion concentration measurement can be performed continuously, but the electrode structure is complicated and special. Measurement requires punching and is not suitable for continuous measurement.In electrical conductivity measurement, when the liquid to be measured for concentration flows, the liquid on the surface of the measurement electrode is disturbed, and the electrode becomes polarized, causing problems during repeated measurements. has disadvantages such as the tendency to cause unsteadiness.

[Object of the Invention] It is an object of the present invention to improve the above-mentioned drawbacks of the prior art and to provide an inexpensive device for repeatedly and continuously measuring and monitoring the concentration of a liquid.

<Structure of the Invention> The continuous fluid concentration measuring device of the present invention is a device that immerses a pair of electrodes in a liquid to be measured and electrically measures the impedance between the electrodes, in which a pulse voltage is applied between the electrodes. It is characterized by having been configured.

<Example> An example of the present invention is illustrated by the electric circuit block diagram shown in FIG. 1 and other figures.

The concentration measuring device of the embodiment includes a voltage applying means 1 that generates and outputs a pulse voltage e, a pair of concentration detection electrodes (ρ) immersed in a liquid whose concentration is to be measured, and an auxiliary resistor (RA).
A liquid concentration detection means 2 which receives the pulse voltage output C of the pulse voltage application means 1 and outputs the inter-electrode potential difference C' as a concentration detection signal from the electrodes BC between the electrodes (pl); The measurement means 3 receives the output C' in a comparator circuit 17, compares it with a preset reference voltage 18, performs arithmetic operations in an arithmetic circuit 19 if necessary, and outputs the result to an output circuit 20.

An example of the structure of the electrode (1) in the detection means 2 is shown in FIG. The electrode P has a concentric rod shape as shown in the sectional view taken along line A-A, and since it is used in a conductive liquid, it is made of a corrosion-resistant conductor, such as graphite or stainless steel mesh.

Further, to describe the configuration of the pulse voltage applying means 1 in more detail, the means is constituted by a power source 11, a switching circuit 12 connected to the power source 11, and a control circuit thereof.

The switching circuit 12 consists of a switch element 13 that opens and closes the circuit ON-OFF, and a polarity change element 14 that changes the polarity of the input from the power supply 11. Each element has a one-shot pulse generation circuit 15 that controls each element, and a polarity change element 14 that changes the polarity of the input from the power supply 11. A conversion control circuit 16 is connected.

Next, the effect will be explained.

In the pulse voltage application means 1, the switching circuit 12 is turned on by the square wave generated by the one-shot pulse generation circuit 15, and a square pulse voltage e having a short pulse width is applied between the circuit AC of the detection means 2. Ru. In the same circuit, BC between electrodes (ρ) immersed in the liquid whose concentration is to be measured
An impedance determined by the concentration of the liquid occurs,
This is connected in series with the auxiliary resistor (RA), and the rectangular pulse voltage C is applied to this series connection circuit ABC. Therefore, if the partial pressure value e' between 80 and 80 of the rectangular pulse voltage C is measured, the liquid Concentration can be detected. When the detection means 2 outputs the interelectrode potential difference e' as a liquid concentration detection signal, the measurement means 3 receives it in the comparison circuit 17 and compares it with a preset reference voltage 18, or if necessary, sends it to an arithmetic circuit. In step 19, the comparison results are further subjected to calculations, converted into numerical values, and outputted to the output circuit as liquid concentration determination data or measurement data.

In this way, -th concentration measurement is completed. In order to repeatedly and continuously perform this measurement, the above-mentioned applied pulse voltage e
As shown in FIG. 4 (al), the detection means 2
is applied to the input circuit AC.

FIG. 2 shows the measurement results according to this example.
It is not shown that the interelectrode potential difference C' is inversely proportional to the liquid concentration. This data shows that the concentration of the liquid can be easily measured by detecting the potential difference between the electrodes and performing calculations and other processing on this.

Normally, when a voltage is applied to an electrode, an electrochemical reaction begins immediately after the voltage is applied. First, ion adsorption occurs for a short time near the electrode, then ion precipitation occurs on the electrode surface,
Gas is generated at the anode and metal is deposited at the cathode. Therefore, when there is a flow of liquid on the electrode surface, ion precipitation is disturbed, which affects the potential difference between the electrodes. As a result, it becomes difficult to measure the concentration of the liquid, and the reproducibility of the measurement cannot be achieved.

However, in the present invention, the voltage application to the electrode is completed in an extremely short time, and the reactions at the electrode during this time only result in a small amount of ion adsorption near the electrode and a similarly small amount of charging of the electrostatic container. Therefore, with this level of electrode reaction, the electrode potential is not disturbed by the flow of the liquid, and the device of the present invention allows
Even when the liquid is flowing, the concentration of the liquid can be accurately measured. Furthermore, no gas generation or polarization occurs during measurement.

In the above embodiment, when the voltage of the power supply 11 is applied to the input circuit AC of the detection means 2 through the switching circuit 12 as a one-shot rectangular pulse voltage e, further:
When the polarity switching control circuit 16 is activated, the polarity of the voltage C applied to the detection means 2 can be switched.

As shown in Figure 4(b), the polarity of this applied voltage is changed for each concentration measurement, or as shown in Figure 4(C), the polarity is changed during - measurement period. By doing so, the electrode surface can be kept constantly fresh. Therefore, analysis and precipitation reactions on the electrode surface can be further suppressed, allowing accurate concentration measurement.

In addition to the concentric shape shown in the embodiments, the electrode structure in the present invention can be of a free structure such as parallel versus isomorphic, and the comparison calculation means can be an integrated circuit such as a comparator or a microcomputer circuit. This can be realized using a circuit.

Regarding the liquid concentration detection means, in the embodiment, a pulse voltage of a certain magnitude is applied to a circuit in which an interelectrode impedance and an auxiliary resistor are connected in series, and the potential difference between the electrodes is detected. Alternatively, it is also possible, for example, to apply a constant current pulse to the circuit to generate a potential difference between the electrodes and detect it.

<Effects of the Invention> When the concentration measuring device according to the present invention is used, an extremely short pulsed voltage is applied to the electrode for measuring the concentration, so disturbances and polarization effects on the electrode surface due to liquid flow are extremely short. It takes a long time and has little effect on measurement accuracy. Therefore, with this device, it is possible to accurately measure and monitor the concentration of a liquid in a very short period of time or repeatedly and continuously.

[Brief explanation of drawings]

All drawings depict embodiments of the invention. Fig. 1 is an electric circuit block diagram, Fig. 2 is an explanatory diagram of the operation of the embodiment of the present invention, Fig. 3 is an explanatory diagram showing the electrode structure, and Fig. 4 is a time chart showing the voltage waveform applied to the detection means. be. ■-Pulse voltage application means 2-Detection means 3-Measurement means
11-Power supply 12-Switching circuit 15...-One-shot pulse generation circuit 16-Polarity change control circuit 17-Comparison circuit 19-Arithmetic circuit 20~ Output circuit

Claims (1)

[Scope of Claims] (11) An apparatus for electrically measuring impedance between a pair of electrodes by immersing them in a liquid to be measured, characterized in that a pulse voltage is applied between the electrodes. (2) The continuous concentration measuring device for a fluid according to claim 1, which is configured to change the polarity of the pulse voltage applied to the electrode for each measurement. (3) - times 2. The continuous fluid concentration measuring device according to claim 1, wherein the device is configured to change the polarity of the pulse voltage applied to the electrode during the measurement period.