SU1672304A1 - Device for measuring the size of particles suspended in a liquid medium - Google Patents

Abstract

This invention relates to a measurement technique. The aim of the invention is to improve the measurement accuracy by providing automatic electrical calibration. The device contains a power source for the sensor and an amplifier (V) for the pulses of the detecting circuit, made with control inputs, an analyzer (A) for the amplitudes of the pulses and a control circuit including a circuit for stabilizing the amplitudes of the pulses. At the source output, a calibration signal ΔI is formed, and the gain K, K, is adjusted as the measurement conditions change. K is controlled by a signal from a pulse amplitude stabilization circuit. At the same time, a stable amplitude signal is obtained at the input A, corresponding to a particle of a certain size. 2 hp f-ly, 2 ill.

Description

This invention relates to a measurement technique, is intended to control the composition of liquid media and can be used in the chemical and other industries.

The aim of the invention is to improve the measurement accuracy by providing automatic electrical calibration of the device, as well as improving its performance characteristics by providing a control mode for the power source of the sensor.

FIG. 1 shows a functional diagram of the device; FIG. 2 - timing diagrams explaining the operation of the scheme.

The device contains a detecting circuit 1, an analyzer 2 pulse amplitudes

and a circuit consisting of a power supply source 3 of the sensor and a control circuit

The conductometric patchik consists of vessels 4 and 5 and electrodes b and 7. Electrode 6 and vessel 5 are lowered into vessel 4, and electrode 7 is lowered into vessel 5. In the wall of the latter, there is an opening of a regular cylindrical shape, hereinafter referred to as aperture 8. Electrodes 6 and 7 are placed on both sides of the aperture 8 and form an electrochemical cell when the suspension of the test powder is poured into the vessel 4 in the appropriate electrolyte. The vessel 5 is connected to a vacuum source that creates a flow of suspension from the vessel 4 to the vessel 5 through the aperture 8, providing ohozhdenie powder particles through the test

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aperture 8. wherein the concentration of particles in the suspension is chosen small enough so that the probability that two or more particles pass through the aperture 8 simultaneously is negligible.

The output of the sensor power supply 3 is connected to the sensor electrode 6 and to the input of the detecting circuit 1, and the sensor electrode 7 is connected to the common power supply bus. The detection circuit 1 consists of a capacitor 9 and an amplifier 10 pulses. The input of the circuit 1 is the first plate of the capacitor 9, the second plate of which is connected to the input of the amplifier 10, and the output of the latter is the output of the circuit 1.

Sensor power supply 3 and amplifier

The 10 pulses of the detection circuit 1 are made with control inputs. The input of amplifier 10 controlling the magnitude of its gain factor K is the control input of circuit 1.

The control circuit contains a generator

11 impulses, a pulse amplitude stabilization circuit 12, a source of logic signals 13, AND 14, an inverter 15 and an electrically controlled switch 16. The output of the generator 11 is connected to the first input of the circuit 12 and to the first input of the AND 14 element, the second input of which is connected to the input of the inverter 15 and to the output of the source 13 logic signals. The output element And 14 is connected to the control input of the sensor power supply source 3, and the output of the inverter 15 - to the control input of the electrically controlled switch 16. The normally closed contacts of the latter are connected to the input of the analyzer 2 pulse amplitudes, and the normally open contacts 12. The output of the latter is connected to the control input of the detection circuit 1, the output of which is connected to the common contact point of the electrically controlled switch 16.

The sensor power supply 3 may comprise a voltage source 17, a resistor 18, which is the upper arm of the voltage divider, series-connected resistors 19 and 20, forming the lower arm of the divider, an electrically controlled switch 21, and a current stabilizer 22, the output of which is the output of the source 3 of the power sensor. The output of source 17 is connected to the first output of resistor 18, the second output of which is connected to the input of the current regulator 22 and to the first output of resistor 19. The second output of resistor 20 is grounded, and the normally open contacts of electrically controlled switch 21 are connected in parallel with resistor 20, the control input of which is the control input of source 3. The pulse amplitude stabilization circuit 12 in the control circuit may comprise a synchronous detector 23, a reference voltage source 24 and a control signal generating circuit 25, for example DC power. The first input of the circuit 12 is the control input of the receiver 23, and the second input is the analog input of the detector 23, the output of which is connected to the first input of the control signal generating circuit 25. The second input of the latter is connected to the output of the source 24. At the same time

5, the output of the control signal generation circuit 25 is the output of the circuit 12.

FIG. 2 shows voltage diagrams in calibration mode, explaining the operation of the device,

0 where Un is the voltage at the output of the pulse generator;

Ui3 is the voltage at the output of the source of logical signals;

Uis is the voltage at the input of the current stabilizer at the sensor power supply; Uz is the voltage on the sensor; Ui is the voltage at the output of the detecting circuit with the transmission coefficient of the synchronous detector equal to one,

0Uon24 - set output voltage

reference voltage source in the pulse amplitude stabilization circuit;

Ui2 is the voltage at the output of the pulse amplitude stabilization circuit.

5 The device operates as follows.

The pulse generator 11 supplies the signal Un (FIG. 2) to the first input of the pulse amplitude stabilization circuit 12 and to the first

0 input element And 14, preparing the device to work.

The mode of operation is determined by the source 13 of the logical signals 1M3 by forming a logic zero signal at its output.

5 (Measurement mode) or a signal of a logical unit (Calibration mode).

In the Measurement mode, the UIG signal of the logical zero is fed to the second input of the I14 element and to the input of the inverter 15. This

0 the signal through the inverter 15 holds the contacts of the electrically controlled switch 16 in the position shown in FIG. 1 and simultaneously blocks the flow of pulses from the generator 11 to the control

5, the input of the power supply source 3 of the sensor, leaving the contacts of the electrically controlled key 21 in the open position. In this case, the conductometric sensor is supplied from source 3 with a constant current I, specified by the reference voltage U0ni7 of source 17.

The voltage pulses from the sensor, caused by particles passing through the aperture 8, are fed to the input of the detection circuit 1 and then through the capacitor 9 to the input of the amplifier 10 pulses with an adjustable gain factor K. From the output of the latter, the signals arrive through the output of circuit 1 and the normally closed contacts of switch 16 to the input of the analyzer 2 pulse amplitudes.

In the Calibration mode, the 1Mz signal of the logical unit through the inverter 15 acts on the electrically controlled switch 16, switching its contacts, and simultaneously enters the second input of the And 14 element, allowing the passage of pulses from the generator 11 through the I14 element to the control input of the source 3. In this case the key 21 closes its contacts, short-circuiting the resistor 20 of the voltage divider at source 3. This changes the divider ratio of the divider and creates an increment of the voltage AtJis, which the current stabilizer 22 converts to current change, forming at the source output 3 a current pulse DI. So

AUie as a voltage relation -zuU18

Since the sith only divider divider ratio and does not depend on the voltage Uie, then the corresponding ratio toD1c -: - const and does not depend on the value

current I.

A current pulse D creates a voltage pulse D O on the sensor, which enters the input of the detection circuit 1 and is amplified by the amplifier 10. The amplified pulse Ui is fed through the contacts of the switch 16 to the second input of the amplitude stabilization circuit 12 and then to the analog input of the synchronous detector 23. The control input of which receives the Un signal from the first input of the circuit 12. The synchronous detector 23 may contain a series-connected sample-storage circuit and a low-pass filter. By averaging the pulses upon detection, the effect on the measurement result of pulses randomly distributed in time is eliminated. The low-pass filter of the synchronous detector 23 isolates a constant voltage proportional to the amplitude of the pulse at the output of the detecting circuit 1. The control signal generating circuit 25 compares this voltage with the reference reference voltage U0n24 of source 24 and produces a regulating signal Ui2. The last comes from you

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device 25 through the output of the circuit 12 and the control input of the circuit 1 to the control input of the amplifier 10, changing its gain i factor K so that the voltages at the inputs of the circuit 25 are equal. Thus, when a current pulse is applied to the sensor the values of D I scheme provides, at a constant ratio

D |

currents - g - equality of the output voltage 1H of the detection circuit 1 to a predetermined constant value Uon24. which allows to eliminate the influence of the resistivity of the electrolyte on the measurement result and thus the independence of the amplitude of the pulses at the input of the analyzer 2 from the sensor parameters is achieved. The execution of the second source 17 of the reference voltage with the control input allows the absolute magnitude of the current I of the sensor and the pulse of the current of the DG to be adjusted at the output of the sensor power supply.

Claims (3)

Claim 1. Device for measuring the size of particles suspended in a liquid medium, comprising a conductometric particle size sensor with two electrodes, a detection circuit, a pulse amplitude analyzer, a sensor power supply and a control circuit, the first electrode being connected to a common power rail, and the second electrode connected to the output of the power source of the sensor and the input of the detecting circuit, consisting of a series-connected capacitor and amplifier, which, in order to improve the accuracy and measurement by providing automatic electrical calibration, the control circuit comprises a pulse generator, a source of logic signals, an inverter, an And element, a synchronous detector, a first reference voltage source, a control signal generating circuit, and an electrically controlled switch, the output of the source of logical signals being connected to the input of the inverter and the first input of the element I, the output of which is connected to the control input of the sensor power supply, the output of the inverter is connected to the control input of metrically controlled switch, normally closed contact which is connected to the input pulse amplitude analyzer, a normally open contact coupled to the second input of the synchronous detector, the output of the detecting circuit connected to the common point contacts electrically controlled switch, the synchronous detector output is connected to the first input of the control circuit formation Sigma, to the second input of which the output of the first reference voltage source is connected, and the output of the control signal generation circuit is connected to the control input of the detecting circuit to which the control input of the amplifier is connected, and the output of the pulse generator is connected to the second input element And the first input of the synchronous detector. 2. The device according to claim 1, wherein the power source of the sensor comprises a second reference voltage source, first, second and third resistors, an electrically controlled switch and a current regulator, the output of which is the output of the sensor power source, the output of the second source of reference voltage is connected to the first output of the first resistor, the second output of which is connected to the input of the current regulator and to the second and third resistors connected in series, the second output of the first resistor being connected to the first A second resistor is connected to the second resistor, and a common supply bus is connected in parallel to the third resistor. An electrically controlled switch is normally open, the control input of which is the control input of the sensor power supply. 3. The device according to PP. 1 and 2, so that, in order to improve performance by providing a control mode for the power source of the sensor, the output of the control signal generation circuit is configured to be connected to an additional control input of the power source of the sensor, connected to the control input of the second source of the reference voltage. R 1 and eleven p p p p p p p p U, a FIG. g