SU670906A1 - Potentiometric sensor - Google Patents

Description

The invention relates to electrical measuring technology, more precisely to sensors, which serve to measure the electrical resistivities of conductive sheet and film materials and coatings. A device is known for determining the electrical resistivities of conductive materials, in which four-electron potentiometric sensors are used for measurement, containing rod-shaped current and voltage electrodes located symmetrically relative to the sensor center on the same line 1. The device is used to measure samples one can imagine a semi-infinite homogeneous isotropic medium. The closest technical solution to the present invention is a power sensor with four linear electrodes, and two potential electrodes can freely move along the length of sample 2. The sensor has the disadvantage of low measurement accuracy, because, first, the sensor determines the resistance of face in one direction (along the length of the sample), therefore, in the case of anisotropic materials, when preparing samples to determine the resistance, it is necessary to know the direction of the main axes of the anisotrop opium, which is not always possible without additional research; secondly, the formula for determining the resistivity includes the linear dimensions of the electrode system, which increase the measurement error. The purpose of the invention is to increase the measurement accuracy. The goal is achieved in that the current and voltage electrodes are made in the form of rods with rounded ends, which are located on the same line and are symmetrical about the middle distance between the current electrodes. An additional third electrode is located off the other electrodes at the vertex of the straight fragile of an isosceles triangle, the other electrodes of which are current electrodes. To ensure the reliability of the contact of the point electrodes and the stability of the sensor relative to the surface, there is no need for current, the current electrodes and the additional voltage electrode are rigidly fixed on a common base, and the electrodes are naively relative to them on flexible supports.

Fia FIG. 1 shows a drawing of a possible design of the proposed potentiometric sensor, section LL; in fig. Figure 2 shows the theoretically calculated dependence of the ratio of the voltage between the additional electrode and any voltage electrode (U) to the voltage between the two potential electrodes (LJ) on the angle of rotation of the potentiometric sensor relative to the anisotropy axes (a) for an anisotropic material with an anisotropy factor of / (0, 66. On the graph plotted such points obtained experimentally.

The sensor body is made of two disks of Plexiglas / connected to the metal ring with 2 screws 3. On the lower disk there are rigidly fixed current electrodes 4 and an additional electrode electrode 6. Electrodes of the voltage 5 and can move in the holes of the upper and lower disks, and in the off position, the electrodes 5 are fixed with the help of rings 7. The elastic pressing is carried out with the help of springs 8. The supply nodes (not shown in the figure) are connected to the electrodes with the help of nuts 9 or soldering.

The work of the proposed potentiometric sensor can be described as follows. The dependence of the voltage ratio on the angle of rotation of the sensor is recorded as

U (U

And c, nor, r / r- (l-sin2a) + (l-Lsin2a)

 0.5-f 0.361 n., -. ----: -7Г,

I I- (1 + sin 2a) + (1-sm2a)

The maximum value of .- is obtained

a -H-l / g (n 0. ± 1 ±, 2 ...), which is evident from

the pattern in FIG. 2, therefore, the position of the sensor corresponding to the maximum value of U is chosen first, since it does not depend on the angle of rotation. This makes it possible to determine the direction of the anisotropy axes.

By knowing the value of U, U and the current between the current electrodes, it is possible to determine the resistivity of conductive anisotropic sheet and film materials and coatings using the following formulas:

TSZ and

 R.x Rgu l

{nlY

LT

-.TO; .б9з

and

Specific electrical Sogde p.v, ru opposition in the direction of the city of pgry no PTPin:

b is the thickness of the material or coating;

y is the current between the current electrodes; / С - anisotropy coefficient;

and - voltage between potential electrodes;

U is the voltage between the additional electrode and any potential electrode at the angle of rotation of the sensor;

n - coefficient taking into account the limitations of the material under study but the width

2 L n & rci j,

where L is the width of the material;

D is the distance between the current electrodes;

c is the base of the natural logarithm.

The use of a sensor with point electrodes makes it possible to determine the electrical resistivity directly on the materials without preliminary preparation of special samples. The introduction of an additional voltage electrode allows the characteristics of anisotropic conductive materials and coatings to be determined.

A potentiometric sensor with five-point electrodes can be used in the chemical industry, engaged in the manufacture of current-conducting materials, such as conductive rubbers, fabrics, films, papers, etc. The sensor can be used to determine specific electrical resistances or thicknesses. (since there is an unambiguous relationship between the resistances of the material and its thickness) of conductive coatings applied to structures made of conductive materials, for example, fiberglass to remove electrical static charges that form on the surface of the product during its operation.

Claims (2)

1. Potentiometric sensor for determining the resistivity of conductive materials, containing two current electrodes and two voltage electrodes, characterized in that, in order to improve the measurement accuracy, the sensor is equipped with a voltage supplementary electrode, and the additional and current electrodes are sealed on a common basis hard, and the voltage electrodes - poppine n ppp x 2. A sensor according to claim 1, characterized in that the additional electrode is located at the apex of the n-angle of an isosceles triangle and formed with current electrodes. Sources of information taken into account in the examination: 1. M. A. Berliner, Measurement of Humidity. M., Energie, 1976, p. 53-54. 2. GOST 20214-74.