SU1569566A1 - Apparatus for measuring level of conducting media - Google Patents

Abstract

The invention is intended to measure the level of electrically conductive media and allows for improved measurement accuracy by reducing the effects of pickup and leakage current. Under the action of an alternating current source 3 at the inverting input of the operational amplifier 5, which is connected to the output of the source 3 through the electrode 1, the liquid 7 and the electrode 2, a voltage arises, and at the output of the amplifier 5 an antiphase voltage. At the same time, through the system electrode 1, liquid 7, electrode 2, negative feedback of the operational amplifier 5 is performed. The information level parameter is the voltage between the connection point of the AC source 3 to the electrode 1 and its common bus with the operational amplifier 5, which is measured It is measured by a voltage meter 4. 1 il.

Description

type 2, is almost equal to the full-, "if the measured value of the level height is 10 times smaller than the maximum measured value,

the fault of the voltage released on the immersed part of the electrode 1, since the difference in the distances from the electrode 9 to the ends of the immersed part of the electrode 1 is negligible compared with these distances

So, the potential of electrodes 2 and 9 relative to the lower end of electrode 1 is determined by the formula (0. But U is almost equal in magnitude to the potential acquired by the lower end of electrode 1 relative to the common bus and measured by a voltmeter 40. Let us show this using a combination of obvious ratios

U1 I0R0-4 U

out

-kig and "w"

U4 U + C,

U, is the potential of the lower end of the electrode 1 relative to the common bus 6;

potential of electrode 2 relative to common busbar, coincident. giving with potential inverting input amplifier 5;

Ji

U in

0

the height of the level is 10 times less than the maximum measured value,

h n 1 i. at --- 0.1, the difference is right

parts of expressions (4) and (5) one from

the other does not exceed 0.2%; With increasing h, the accuracy of formula (5) increases. Therefore, it can be argued that when the height of the level varies within fairly wide limits, the output signal detected by meter 4, with a high degree of accuracy, is determined by formula (5), amplitude U does not differ from the output signal in a known device.

But from the formula (3) it follows that the potential U of the second electrode, and hence the potential of the electrode 9 relative to a common tire for any, yes40

45

50

same smallest values

hInR o

-e does not exceed the value of 7 + tG

55

And - TT s

ui - ie

(6)

where Ug is the potential of the electrode 9 relative to the common tire.

This potential at values of -j-, lying in the range of 0.1-1,

It appears 500 or more times less than the potential difference between the electrode 2 and the ends of the submerged part of the electrode 1t defined by formula (5). Therefore, if the electrode 9 has ground contact Q, this again causes only a very small leakage current to the clamped common bus cannot significantly affect the pattern of streamlines in a liquid.

Claims (1)

Invention Formula A device for measuring the level of electrically conductive media, comprising five Two parallel, vertically mounted electrodes, the first of which is connected at one end to the first output of an alternating current source and to the first input of a voltage meter, characterized in that, in order to increase the level measurement accuracy by reducing the effects of interference and leakage, an operational an amplifier whose output is connected to the other end of the first electrode, the inverting input is connected to the second electrode, and the non-inverting one, together with the second output of the AC source and the second input of the meter direct voltage are connected to the common bus of the operational amplifier.