JPH0820391B2 - Constant current circuit for fluid resistance measurement - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current circuit for measuring fluid resistance, which measures the concentration of solid particles and the amount of bubbles mixed in a fluid and the conductivity of the fluid.

[0002]

2. Description of the Related Art A conventional constant current circuit is, for example, a "linear I
As shown on page 19 of "C Circuit Technique" (Ohm Co.), the current value is controlled based on the voltage obtained from only one current detecting resistor means.

[0003]

A method for constructing a constant current circuit in which the current value is controlled based on the voltage obtained from only one current detecting resistance means as described above is used in the first electrode 1 and the second electrode. A pair of main electrodes a composed of the electrodes 2 of
In order to make the potential distribution between the electrodes uniform, a pair of auxiliary electrodes b, which are composed of a third electrode 3 and a fourth electrode 4 on the left and right of the main electrode a.
An electrode body c for measuring fluid resistance, which is formed by attaching b to the adjacent state, is immersed in the fluid, or is installed on the flow path of the fluid or on the inner wall of the liquid tank, and a constant current is passed between the main electrodes a to make the main electrode a When adopted as a constant current circuit for measuring fluid resistance, which measures the resistance value of the solid-liquid mixture or the gas-liquid mixture or the gas-solid mixture between the main electrodes a by the potential difference between them, the liquid or the multiphase fluid between the main electrodes a A large error may occur in the resistance value of the fluid containing lumps.

That is, when a fluid mass having a conductivity different from that of the surroundings partially exists in the fluid between the main electrodes a or in the multiphase fluid, the resistance value measured greatly varies depending on the position where the fluid mass exists, and the resistance is There may be a large error in measuring. The reason why the measured resistance value differs due to the difference in the positions of the fluid masses having different conductivity between the main electrodes a will be described below with reference to FIGS. 3 and 4.

3 and 4 show the state of the current flowing between the electrodes by lines of electric force.

The third electrode 3 of the auxiliary electrode b is supplied with the same voltage as that of the first electrode 1 of the main electrode a, and the fourth electrode 4 of the auxiliary electrode b is supplied with the second electrode 2 of the main electrode a. Is supplied with the same voltage as.

The current detecting resistor means 7 is connected to, for example, the main electrode a.
It is assumed that the second electrode 2 is set on the side of the second electrode 2.

As shown in FIG. 3, it is assumed that a fluid mass having a conductivity lower than that of the surrounding fluid is near the surface of the first electrode 1. The first electrode 1 because it is hindered by this fluid mass
The current passing through is less than the current passing through the second electrode.

On the contrary, if the fluid mass whose conductivity is smaller than that of the surrounding fluid is near the surface of the second electrode, the fluid mass hinders the fluid mass. Therefore, as shown in FIG.
The current passing through is smaller than the current passing through the first electrode 1. However, in both cases, control is performed so that the current passing through the current detection resistance means 7 becomes a constant value, so when a fluid mass having a conductivity lower than that of the surrounding fluid is near the surface of the first electrode 1. , The resistance value is measured smaller due to the lower voltage applied between the main electrodes a, and conversely when such a fluid mass is near the surface of the second electrode 2, it is applied between the main electrodes a. Due to the high voltage applied, the resistance value is measured as a larger value.

The inventor has found that when a fluid mass having a conductivity different from that of the surroundings partially exists in the fluid between the main electrodes a, there is almost no effect on the difference in the position where the fluid mass exists between the main electrodes a. I devised a method that can measure the resistance value of.

[0011]

The gist of the present invention will be described with reference to the accompanying drawings.

A pair of main electrodes a consisting of the first electrode 1 and the second electrode 2, and a pair of auxiliary electrodes b and b consisting of a third electrode 3 and a fourth electrode 4 on the left and right of the main electrode a. A fluid resistance measuring electrode body c configured by being attached in close proximity is installed in the fluid or in the flow path of the fluid or on the inner wall of the liquid tank, and a constant current is applied between the main electrodes a to provide a space between the main electrodes a. A constant current circuit for measuring fluid resistance for measuring a resistance value of a fluid or solid-liquid mixture or a gas-liquid mixture or a gas-solid mixture between the main electrodes by the potential difference of the first electrode 1 of the main electrode a. Side and the second electrode 2 side are respectively provided with current detection resistance means 7, and the current value is controlled based on the voltage obtained by averaging two voltages obtained from the respective current detection resistance means 7. The present invention relates to a constant current circuit for measuring fluid resistance.

[0013]

When a fluid mass having a conductivity different from that of the surrounding fluid between the main electrodes a is located at an intermediate position between the first electrode 1 and the second electrode 2, a current passing through the first electrode 1 The magnitude of the current passing through the second electrode 2 is equal, and the resistance value between the main electrodes a is correctly measured.

It is assumed that a fluid mass having a conductivity lower than that of the surrounding fluid is near the surface of the first electrode 1. At this time, the current passing through the first electrode 1 is smaller and the current passing through the second electrode 2 is larger than that at the center. However, the average value of the current value passing through the first electrode 1 and the current value passing through the second electrode 2 is not so different from that at the center.

On the contrary, if a fluid mass having a conductivity lower than that of the surrounding fluid is near the surface of the second electrode 2, then it passes through the first electrode 1 at that time as compared to when it is at the center. The current is large and the current passing through the second electrode 2 is small.

However, the average value of the current value passing through the first electrode 1 and the current value passing through the second electrode 2 is not so different from that at the center.

As described above, the current detecting resistor means 7 is installed on both sides of the pair of electrodes 1 and 2 constituting the main electrode a, and the average value of the two voltages obtained from the respective current detecting resistor means 7 is set. By controlling the current value based on the above, even if there is a fluid mass having a conductivity different from that of the surrounding fluid between the main electrodes a, the main electrode is hardly affected by the difference in position. The resistance value between a can be measured.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are block diagrams showing the basic configuration of the present invention. Reference numeral 5 is a differential amplifier, 6 is an amplifier, 8 is a resistor, and 9 is a resistor.

Reference numeral 10 is a water tank for measuring the fluid resistance value. The water tank 10 has internal dimensions of 20 cm in length, 60 cm in width, and 45 in depth.
Molded with an acrylic resin plate of cm, width 15 cm, height 46 cm, thickness 1 facing the center of the inner wall of the side plate of this water tank 10.
A first electrode 1 and a second electrode 2 made of a stainless steel plate having a width of 15 mm and a height of 15 cm with a distance of 2 mm between the first electrode 1 and the second electrode 2 are provided. 46 cm, thickness 1 mm
Third electrode 3 and fourth electrode 4 composed of the stainless steel plate
Are arranged and electrically connected as shown in FIG. 1 to form an electrode. Filling the water tank 10 with an appropriate amount of water, for measurement test, as a substitute for fluid lumps with different conductivity, a plastic prism with a vertical conductivity of 5 cm, width 6 cm, and height 20 cm.
11 (considered as a fluid mass having a conductivity of zero) is erected vertically on the bottom surface of the water tank 10. The water depth was 12.8 cm and the water conductivity was 122 μs / cm.

While changing the position of the plastic prism 11 along the straight line connecting the centers of the two opposing electrode plates 1 and 2 of the main electrode a (from the second electrode 2 to the surface of the plastic prism 11) The distance between them is d as shown in FIG. 5.)
The resistance value was measured. The current flowing between the main electrodes a was a 5 kHz sinusoidal alternating current, and the current value was 0.5 mA.

FIG. 6 shows the measurement result of the resistance value. The vertical axis represents the resistance value [kΩ] between the main electrodes a, and as shown in the figure, the difference in the resistance value depending on the position of the plastic prism 11 was slight and a substantially constant value was obtained.

[0022]

As shown in FIG. 5, when the resistance value of the plastic prism in the water between the first electrode and the second electrode is measured, the resistance value of the plastic is as shown in FIG. It can be seen that almost constant values are obtained regardless of the position of the prism. In order to further clarify the effect of the present invention, FIG. 7 shows the result of measurement by a constant current circuit according to the conventional method in which the current detecting resistor means is installed only on the second electrode side, in the same manner as the above measurement. It is the result of measurement under the same conditions as those of the circuit used in the measurement of FIG. 5, except that the number of current detection resistance means is only one. It can be seen that the measured values vary greatly depending on the position of the plastic prism.

As described above, according to the fluid resistance measuring method by the constant current circuit of the present invention, even if the fluid contains fluid lumps having different conductivity locally, the resistance is more accurate as compared with the conventional method. The value can be measured.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a basic configuration showing the principle of the present embodiment.

FIG. 2 is a plan view showing installation positions of a main electrode and an auxiliary electrode attached to the water tank of this embodiment.

FIG. 3 is a plan view conceptually showing the state of current flowing between the electrodes of the water tank of this embodiment.

FIG. 4 is a plan view conceptually showing the state of current flowing between the electrodes of the water tank of this embodiment.

FIG. 5 is a plan view for explaining the measurement test of the present embodiment.

FIG. 6 is a graph showing the measurement results of this example.

FIG. 7: Comparative test of this embodiment (measured by a conventional circuit)
It is a graph which shows the measurement result of.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st electrode 2 2nd electrode 3 3rd electrode 4 4th electrode 7 Current detection resistance means a Main electrode b Auxiliary electrode c Fluid resistance measurement electrode body

Claims (1)

[Claims] 1. A pair of main electrodes composed of a first electrode and a second electrode, and a pair of auxiliary electrodes composed of a third electrode and a fourth electrode, which are provided in proximity to the left and right of the main electrode. The configured fluid resistance measuring electrode body is immersed in the fluid or installed in the flow path of the fluid or on the inner wall of the liquid tank, and a constant current is applied between the main electrodes to cause the potential difference between the main electrodes to cause fluid or solid A constant current circuit for measuring fluid resistance, which measures the resistance value of a liquid mixture, a gas-liquid mixture, or a gas-solid mixture, in which current is detected on the first electrode side and the second electrode side of the main electrode, respectively. A constant current circuit for measuring fluid resistance, characterized in that a resistance means is provided and a current value is controlled based on a voltage obtained by averaging two voltages obtained from the respective current detection resistance means.