SU838465A1 - Electrokinetical pressure pick-up - Google Patents

Description

(54) ELECTROKINETIC PRESSURE SENSOR

one

The invention relates to information-measuring technology, and more specifically to measuring variable micropressures.

The known electrokinetic variable pressure sensor is a body divided by a porous dielectric / ka partition into two chambers / filled with an electrokinetic. liquid, such as base. Each Ks1mera is placed on the electrode tl

The magnitude of the potential of the flow of an electrokinetic fluid through a porous partition is directly proportional to the dielectric constant of the fluid, its resistivity, and the zeta potential arising from the interaction of the electrokinetic fluid with a solid. A disadvantage of the known electrokinetic sensors of this type is high (hundreds of kilo-ohms) output resistance, as a result of which disturbances that restrict the ability to measure low pressures are applied to the input of measuring devices connected to them.

The closest to the proposed technical essence is

device, used as an electrokinetic accelerometer of hypersensitivity. In this sensor, two porous partitions are applied, the output signal is removed from the two extreme electrode plates, and the two central plates are briefly interconnected 2.

The disadvantage of this sensor is also

0 is a low sensitivity due to high output resistance.

In connection with this, it is advisable to achieve an improvement in the signal-to-noise ratio in known electrokinetic sensors by decreasing the output resistance, t, i.e. by increasing the area of the porous partition, or by increasing the ratio

0 transfer electrokinetic sensor by more thorough cleaning of the working fluid. However, an increase in the area of the porous partition does not allow for the creation of small-sized structures, and the cleaning of the working fluid is very laborious and possible only to a certain limit. In addition, during storage and operation of the electrokinetic sensor, the working fluid is constantly polluted.

since it is in direct contact with the sensor body, the electrodes and the porous partition, and the liquids, which possess the greatest electrokinetic activity, are very aggressive, since they have a polar structure of molecules. By exchanging (due to contamination of the working fluid, the transmission coefficient can be restored by refilling the sensor with fresh fluid.

The purpose of the invention is to increase the sensitivity by improving the signal-to-noise ratio, expanding the lower limit of the pressure measurement range using an electrokinetic converter, as well as providing the possibility of adjusting the transfer coefficient of the electrokinetic pressure sensor.

This goal is achieved by introducing a constant voltage source and a mid-point resistor, with two extreme electrodes connected to each other through a resistor, a constant voltage source connected to the mid-point of the resistor and the middle electrode, which is connected to a metal case .

The resistance value of the resistor to reduce its shunt effect should be close to the value of the output resistance of the electrokinetic sensor.

The variable output signal can be removed through a capacitor from the outer electrode relative to the grounded housing. In this case, the housing acts as a shield for the signal outer electrodes from external electromagnetic fields.

The drawing shows a diagram of the electrokinetic pressure sensor

The electrokinetic pressure sensor consists of a metal case 1, two porous partitions 2, two external signal electrodes 3, one internal electrode 4, a resistor with a midpoint R, a constant voltage source 5, a glass sleeve b, a glass washer 7 and condenser 8.

Porous partitions and electrodes are assembled in a glass sleeve. Parts of the metal housing are put on the sleeve. The terminals of the electrodes and the hour / g of the metal housing solder to the sleeve with glass frit. In practice, electrokinetic sensor housings are usually made of metal. In the case of a non-metallic body of the sensor, additional electrodes can be pushed into the liquid near the sensor from both sides, which must be closed with the middle electrode.

Electrokinetic sensor works as follows.

At the interface between the working fluid and the surface of the porous septum, an electrical double layer is formed, formed by polar molecules of the liquid oriented in the direction of the solid. Near the double electric layer, ions of one sign, forming an electric charge, attracting ions of another sign, are concentrated in a liquid. Moreover, the lower the concentration of ions in a liquid, the less their connection with the electric double layer, and, consequently, the potential arising from the flow of liquid at the ends of the porous partition occurs. When a source of electrical voltage is connected to the electrodes, the concentration of liquid ions in the capillaries decreases as the ions are collected to oppositely charged electrodes. As a result, the potential that occurs at the end of the porous septum increases when the liquid flows through it, the conversion ratio of the electrokinetic pressure sensor increases. In addition, in the vicinity of the electrodes, when electrical voltage is applied to them, the molecules of the polar liquid are oriented in the direction of the electrode. Moreover, the molecules on both sides of the electrode are oriented towards the electrode by the same poles, i.e. near the electrode, an electric charge arises, created by the like-charged poles of the molecules. With a liquid overflow, this charge shifts towards the overflow, as a result of which the potential induced by this charge on the electrode decreases. The magnitude of this charge is proportional to the voltage of the electric field.

Due to the purification of the fluid from the ions inside the capillaries and the specific orientation of the molecules of the polar fluid near the electrodes to which electrical voltage is applied, the magnitude of the change in the electrode potential increases as the fluid flows, therefore the signal-to-noise ratio improves. By varying the magnitude of the DC voltage on the electrodes, the concentration of ions in the capillaries can be controlled, due to the orientation of the polar molecules near the electrodes, which determine the conversion factor of the electrocution of a non-conventional pressure sensor.

Claims (2)

Invention Formula An electrokinetic pressure sensor comprising a metal housing in which three electrodes are placed, separated from each other by two porous partitions immersed in an electrokinetic fluid, characterized in that, in order to increase the sensitivity. A DC voltage source and a mid-point resistor are inserted in it, the two extreme electrodes are interconnected via a resistor, the DC voltage source is connected to the midpoint of the resistor and the middle electrode, which is connected to the metal case. Sources of information taken into account in the examination 1, Electrochemical converters of primary information. Ed. E.M., Dobrynina and P.D. Lukovets, VA, M., Mashinostroenie, 1969, p. 57, fig. 9. 2. Kasimzadeh M.S. and others. Electrokinetic information converters. M., Energie, 1973, p. 99, fig. 45 (prototype).