SU1334046A1 - Device for measuring the liquid level - Google Patents

Description

The invention relates to electronic measuring devices of automation and can be used to measure the particle size distribution of dispersed products according to the Wigner method using communicating vessels or to directly measure the level of conductive and non-conductive liquids.

A device for measuring the level of a liquid is known, comprising measuring and compensating sensors, an operational amplifier connected to a zero -opraHOMj trigger, two switches and a resistor.

The disadvantage of such a device is low measurement accuracy and limited dynamic range.

The closest to the technical aspect of the invention is a device for measuring the level of a liquid, comprising measuring and compensating level converters connected to the inputs of the forming unit of the counting pulses, to the output of which a pulse counter is connected connected through the unit for correcting the measurement results to the control input of the unit forming counting pulses.

The main disadvantages of this device are low noise immunity, due to the strong influence of amplitude noise on the operation mode of the forming pulse counting unit, and the degree of error compensation due to the final resolution of the comparators is not high enough.

The aim of the invention is to improve the measurement accuracy and improve noise immunity.

This goal is achieved by the fact that in a device for measuring the level of a liquid, containing measuring and compensating level converters connected to the inputs of a block for forming counting pulses, the output of which is connected to a pulse counter connected through a block of correcting measurement results with a control input of a block for shaping counting pulses, the block generation of counting pulses made in the form of a frequency-modulated oscillator with pulse control and synchronization introduced into the device p connected to the output .bloka formed

five

0

five

0

five

0

five

0

five

the correction of measurement results, and four controllable keys from it, the first and second keys being connected between the level converters and the autogenerator inputs, the third key between the pulse counter and the measurement result shaping unit, and the fourth connected to the output of the pulse counter.

The drawing shows a block diagram of the device.

The measuring 1 and compensating 2 level converters are connected respectively via the first 3 and second 4 keys to the oscillator 5, which is made according to a frequency modulated circuit and has a control input for varying the duration of the radio pulses generated. The output of the oscillator 5 is connected to the input of a pulse counter 6, the output of which through the third key 7 is connected to the measurement correction block 8. Block 8 includes a code comparison circuit 9, an error signal generator 10 and a pulse-controlled one, a 1 st generator 1 1, the output of which is connected to a control input of an auto-generator 1 and 5 and a synchronizer input

12. The control circuits of the synchronizer 12 are connected to the inputs of the keys 3, 4, 7, as well as the fourth key 13 connected to the output of the pulse counter 6.

The operation of the device occurs in two cycles (measuring and correcting) as follows.

In the measuring cycle, the measuring transducer 1 is connected through the oscillator circuit of the auto-oscillator 5 through the auto-oscillator circuit 5. The auto-oscillator 5 operates in the key mode, generating oscillation packs (radio pulses) whose length is equal to the duration of the control command sent to its control the input and the frequency of the high-frequency filling is an unambiguous function of the inductance (or capacitance) of the converter, which, in turn, depends on the measured liquid level. In this way, the measured level is converted into the frequency of electrical oscillations and the quantization of the measurement information in time.

At a certain value of the controlled level h, the frequency of electrical oscillations of the oscillator 5 is equal to fy,,

1 pack composition

and the number of oscillations N LET

N. nT

where T is the unadjusted duration of the radio pulse (the duration of the packet of oscillations). If under the action of destabilizing factors at a constant value of h, the frequency changes by 4fj, then the number of pulses in the packet changes to N), J

NI, (f ,, - df) T. (2) and the absolute measurement error will be 4N.

The essence of the measurement error correction method used in the device is reduced to the change in the population of the packet of oscillations so that at a constant value of h the number N showing it remains unchanged despite the influence of destabilizing factors. The corrected duration T, of a radio pulse is found on the basis of expressions (1), (2) from the following relationship:

% t

where

T

 (f. + L.) T,

ck

(3)

fi t

 f. + df

one

----- (4) 1+ tt.

The number code.N, in the measurement cycle, is transmitted to the output of the device via the key 13.

Definition and automatic installation of the corrected duration Tj, | produced in a corrective cycle of operation of the device. In this case, the permit command is removed from the control input of the switch 3 and the enable commands are given to the keys 4, 7. The compensation converter 2 is included in the circuit of the oscillator 5 via the switch 4. The oscillation frequency of the oscillator 5 is determined by the inductance of the converter 2 and equal to the duration of the command at its control input:

NKOM com. T., (5) is the frequency of the autogenerator 5 when a compensating converter is included in its circuit 2.

where f.

6

The control of the h; 1s of oscillations in time T is carried out by the circuit 9 of the comparison of codes, in the memory of which the recorded during calibration of the device is stored

number N

kom. about

Under the action of destabilizing factors, the equality N N, "", 0 is violated.

0

five

-N Whom com. about

five

The difference code dM N influences the error signal shaping circuit, generates a voltage that controls the duration of the pulses of the controlled oscillator 11. At the same time, despite the change in the frequency- f, by the value of af (

- rk

f

com

T (, „„ - ь f) T

ck

(6)

from where

T

CV

, kn m

(7)

s 25

For the oscillator. In a wide frequency range, the equality

Af fli.

Of

com comparison

B (4)

(eight)

and (7) subject to

thirty

35

40

45

50

(8) it follows that 1 ;, T., i.e. with the correction of the error in the correction tact, the correction of the error is achieved in the measuring tact of the device. If, under the action of destabilizing factors, the frequency of the oscillator decreases, the duration of the radio pulse increases until the previous number of high-frequency oscillations is placed in it. Similarly, the duration of the radio pulse decreases as the frequency of the high-frequency filling increases.

The error signal found in the correction cycle is stored and used to control the pulse duration of the controlled oscillator 11 pulses in the measuring tact of the device.

The feasibility effect is expressed in improving noise immunity and accuracy, which allows increasing the reliability of the device and expanding its scope in controlling dispersed products.

Output

Editor M. Tsitkina

Compiled by Yu.Korshunov

Tehred M. Didgk Proofreader E. Roshko

Order 3955/40 Circulation 693 Subscription

VNIIGO State Committee of the USSR

ABOUT

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

- --.- --..- -, -.-. - - - .. -.-.- .. -. - - 1. "--r - - - - - --.-

Production Printing Enterprise, Uzhgorod, Proektna St., 4

Claims (1)

A DEVICE FOR MEASURING A LIQUID LEVEL, containing measuring and compensation level converters connected to the inputs of a counting pulse forming unit, the output of which is connected to a pulse counter connected through the unit for generating correction of measurement results to the control input of a counting pulse forming unit, which is characterized by In order to increase the accuracy of measurements and improve noise immunity, the unit for generating counting pulses is made in the form of a frequency-modulated oscillator with pulses control and a synchronizer is inserted into the device, connected to the output of the correction unit for forming the results of measurements, and four keys controlled from it, the first and second keys being connected between the level converters and the inputs of the oscillator, the third key between the pulse counter and the unit for generating results measurements, and the fourth is connected to the output of the pulse counter. SU „„ 1334046