SU574625A1 - Micrometering device - Google Patents

Description

on, adjacent to the lower portion of the horizontal knee.

FIG. 1-2 shows the proposed microdispenser.

The microbatcher includes a gas pipeline 1, a capillary p 2 with two V-shaped bends, one of which 3 is horizontal and the other 4 is vertical, as well as three capacitive sensors 5, 6, 7 and switch 8. The sensors are installed in such a way that the cavity between the plates of one of them 5 (tank Ci) is filled with metered liquid, the other 6 (tank C3) is filled with gas, and in the cavity of the third one there is 7 (tank Cz). There is a vertical meniscus of the liquid. The electrodes of the sensors are connected to the input of the switch 8.

The dispenser works as follows.

A diluent gas is supplied to the inlet of the pipeline 1 with a predetermined flow rate, into which a vapor of liquid diffuses from the capillary 2. At the exit of the pipeline 1, after the expiration of a certain period of time from the moment the diluent gas is supplied, a vapor-gas mixture of constant composition is formed. The amount of evaporated liquid is based on the known diameter of the capillary 2 and the displacement of the position of the meniscus of the liquid. To determine the displacement of the vertical meniscus position of the fluid, the constant values of the capacitances Ci and C3 and the variable magnitude of the capacitance Cz are measured. The measurement is carried out by connecting capacitive sensors in series with a switch 8 to the input of the measuring device.

The change in the position of the meniscus is found in relation (1) below. The highest accuracy of the position of the vertical meniscus is achieved with a special implementation of the capillary 2 and sensors 5, 6, 7 coaxial with the possibility of completely filling the sensor cavity with metered liquid. The plates 9 and 10 of each sensor are formed by the metallized axial part and the inner wall of the outer part of the coaxial capillary 2. For this case, it is not difficult to find a connection between the displacement of the vertical meniscus and the values of the capacitances of the sensors.

 (x - So) I

x-fl

with,

2g „

2

IL / (

Sz

four

where the BZ and bio-dielectric permeability of the dosed liquid and gas in the capillary channel 2, respectively;

In is the height of the plates of the sensor;

2

- - relation of external and internal raIl

sensor cover plates. With / J / j /, 1, we have C, - C

/.

/ z

(one)

s, s

V- / I-3

As can be seen from the ratio, to determine the value / there is no need to find the value of the dielectric constant of the metered liquid.

Thus, the introduction of three capacitive sensors into the device makes it possible to increase the accuracy of determining the position of the liquid meniscus during metering and the accuracy of determining the composition of the vapor-gas mixture associated with it. Due to the high sensitivity of the capacitive method for determining the position of the liquid meniscus, the time interval required for

determination with the required accuracy of the position of the meniscus can be significantly reduced compared with the option of visual reference.

Claims (3)

1. Kollerov DK Metrological foundations of gas-analytical measurements, M., “Standartizdat, 1967, p. 174. 2. US patent number 3540277, cl. G 01F 23/26. 1970. 3. The copyright certificate SSSR 166163, cl. G OliN 31/08, 1963.