RU2092824C1 - Method of measuring the aqueous-oil emulsion moisture content and device intended for its realization - Google Patents

Abstract

FIELD: automatic control systems. SUBSTANCE: resonant circuit the capacitance of which depends on moisture content of emulsion is excited by AC voltage at several frequencies. Amplitude of resonant circuit oscillations is recorded for every frequency the number of which is n ≥ 3. Inherent resonant frequency of circuit is calculated from measured values. Emulsion moisture content is judged by inherent resonant frequency of circuit. Device has resonant circuit 6 connected to detector 7. It is also connected to amplifier 4 through two-wire connecting line 5. Device is also provided with controlled generator 3, controller 1, digital-to-analog converter 2, analog-to-digital converter 8, and indication unit 9. EFFECT: higher accuracy of measurement.

Description

 The invention relates to automation and can be used for remote control of oil moisture.

 A known method and device for controlling humidity, including the excitation of the resonant circuit voltage from the generator and the registration of the oscillation frequency (1). A disadvantage of the known method and device for measuring humidity is the need to maintain a strictly defined value of mutual induction between the inductor and the resonant sensor during the monitoring process.

 The closest technical solution to this is the method and device for controlling oil moisture, including the excitation of the resonant circuit and recording the frequency of natural oscillations, which is used to judge the oil moisture. For this, a constant frequency generator is connected to an inductor, which is oriented relative to the resonant circuit. In the latter, oscillations are excited and fed to a filter, which only passes its own oscillations in the circuit and does not pass the rest. Using the keys, the signal passes to the indicator, which gives information about the moisture or “dryness” of the oil (2).

 A disadvantage of the known method of the device is that they do not have high accuracy, since the resonant circuit is excited by a constant frequency generator, therefore, the "frequency" of the generator is possible, which leads to inaccurate measurements.

 The aim of the invention is to improve the accuracy of remote measurement.

 This goal is achieved by the fact that in a method for measuring the moisture content of oil-water emulsions, including excitation of a resonant circuit and recording the frequency of its natural oscillations, which are used to judge the moisture of oil-water emulsions, the resonant circuit is excited by a controlled generator and records the amplitude of oscillations of the resonant circuit at different frequencies, the number of which ≥3, while the generator frequency is fixed and measured at the time of recording the amplitude of the oscillations of the circuit. Using these measurements, the resonance frequency is calculated, which determines the moisture content of oil-water emulsions.

 The specified sequence of actions is carried out with obtaining increased accuracy during remote measurement by the following technical means.

 A device for measuring the moisture content of oil-water emulsions, containing an indication unit, a resonant circuit and a detector, is equipped with a controller, an analog-to-digital converter (ADC), a digital-to-analog converter (DAC) controlled by a generator and an amplifier, while the resonant circuit is connected to a detector, the output of which through a communication line through the ADC is connected to one of the inputs of the controller, the first output of which through series-connected DACs, a controlled oscillator, amplifier and communication line is connected to the resonant circuit, W The other output of the controller is connected to the display unit, the second input of the controller is also connected to the output of the amplifier.

 The drawing shows a functional diagram of the device and the amplitude characteristic of the resonant circuit. The device comprises a controller 1, the first output of which is through a series-connected DAC 2, a controlled oscillator 3, an amplifier 4, and a communication line 5 connected inductively or capacitively to a resonant circuit 6, which is connected to a detector 7, the output of which is connected through an ADC 8 to controller 1 the output of which is connected to the input of the display unit 9, and the second input of the controller is also connected to the output of the amplifier.

 The device operates as follows.

 Changing the capacitance of the resonant circuit changes its resonant frequency, which is an information parameter for determining the moisture content of oil.

 The frequency code of the exciting voltage for the "swinging" of the resonant circuit 6 is generated in the controller 1 according to a special program and fed through one of its outputs to the DAC 2, where the signal is converted to analog and fed to the controlled generator 3. The alternating voltage from the output of the controlled generator 3 is amplified when help amplifier 4 and is fed into a two-wire communication line 5 for the "buildup" of the resonant circuit 6.

 The oscillations of circuit 6 are detected in the detector 7 and transmitted as a constant voltage through the communication line 5 and ADC 8 to the controller 1. The alternating voltage from the input to the two-wire communication line 5 also goes to the second input of the controller 1 to determine its frequency.

 The resonant frequency is determined in the controller 1 as follows.

где
I ток в контуре;
I_max ток в контуре при резонансе;
L,C,R индуктивность, емкость и внутреннее сопротивление контура.Let ω _n and ω be _the resonant frequencies of the resonance circuit in dry oil and water, respectively. In all other cases, the resonant frequency ω _p is between these frequencies. Let at frequencies ω ₁ , ω ₂ ... ω _n belonging to the frequency interval [ω _n ; ω _in ], the amplitude voltages at C _x are measured, which we denote by V ₁ , V ₂ .V _n . The frequencies ω _i can be selected, for example, with a constant step Δω = const.
The resonant frequency corresponds to the maximum of the function V (ω) which is calculated from the points ω ₁ , ω ₂ ... ω _n according to the formula of the generalized resonance curve (EI Nechaev, Fundamentals of Radio Electronics, M. Radio and Communication, 1985, p. 29) :

Where
I current in the circuit;
I _max current in the circuit at resonance;
L, C, R inductance, capacitance and internal resistance of the circuit.

From the formula it is seen that for a unique definition of the type of curve, the quantity n must satisfy the condition n≥3. The maximum point V (ω) will be determined from this data by numerical methods, for example, by taking the first derivative and then determining the point ω _p at which the derivative V ′ (ω) is 0. This or another method suitable for determining the maximum of the function measured in individual points are implemented using the controller program. Next, the moisture content Φ is determined by the resonant frequency and the information is transmitted to display unit 9.

 Thus, the entire algorithm for determining oil moisture consists of the following steps.

1. At the sensor calibration stage, the dependence of the moisture content v on the resonant frequency of the sensor is determined, i.e. dependence v = ω _p (Φ) For this dependence, the range of changes of ω _p when Φ changes from zero to unity is also determined.

2. According to a given program, the controller generates a grid of frequencies in the range of changes w _p and measures the amplitudes of oscillations of the resonant circuit corresponding to these frequencies. The frequency grid can be selected, for example, with a constant step Δω
3. Based on these measurements, the resonant frequency of the circuit is calculated, and then the moisture value Φ corresponding to this frequency is determined from the known calibration dependence v = ω _p (Φ)

Claims (2)

 1. A method of measuring the moisture of oil-water emulsions, including the excitation of the resonant circuit and recording its own resonant frequency, which is used to judge the moisture of oil-water emulsions, characterized in that the resonant circuit is excited at a controlled frequency and the amplitude of oscillations is recorded at different frequencies, which are recorded and measured at the moment recording the amplitude, then using the obtained points, the number of which is not less than three, calculate the resonant frequency of the circuit.  2. A device for measuring the moisture content of oil-water emulsions containing a resonant circuit, a detector and an indication unit, characterized in that it is equipped with an analog-to-digital converter, a digital-to-analog converter controlled by a generator and amplifier, while the resonant circuit is connected to a detector, the output of which is through an analog-digital the converter is connected to one of the controller inputs, the first output of which is through a series-connected digital-to-analog converter, a controlled generator, amplifier, and communication line and connected to the resonant circuit, and the output of the amplifier is connected to the second input of the controller, the second output of which is connected to the display unit.