Method of liquid level detection and device

FIELD: physics, measurement.

SUBSTANCE: invention is related to the field of facilities for automation of different liquids level detection in industrial and household reservoirs, and also for detection of liquids availability and flow in pipelines. Method is based on application of two thermistors that have identical thermal characteristics, and includes heating of one of the thermistors by electric current and its cool-down due to heat transfer to environment, periodic measurement of voltage drop at thermistors, calculation of informative parameter, its comparison with threshold value and making decision on availability or unavailability of liquid at controlled level. At that one of thermistors is periodically heated by short pulses from power supply source. After heating is completed, ratio of non-heated and heated thermistors' voltages are repeatedly measured, and as informative parameter scaled time derivative is calculated by means of specified ratio measurement results array processing. Device for method implementation contains two thermoresistors, which are installed in sensitive element, connected to power supply source and which have temperature resistance coefficients (TRC) of the same sign and identical coefficient of heat emission in gas. Besides, it also contains analog-digital transducer and comparator, reference inlet of which is connected to source of reference signal, and outlet is connected with actuating device. Moreover, device is equipped with pulse switch and serially connected regulator of heating time and synchroniser, and also calculator of scaled derivative. For alarm on liquid flow availability, device is additionally equipped with the second comparator that is connected parallel to the first one, and the second actuating device.

EFFECT: higher efficiency of liquid level detection by increase of device actuation fast-action, reduction of power inputs and expansion of its application field.

13 cl, 3 dwg

 

The invention relates to the field of measurement technology and can be used in the automation of technological processes in various industries, in particular, to automate control of the level of various liquids in industrial and household tanks, as well as to control the availability and flow of liquids in pipelines.

Widely known fluid level indicators, which for deciding on the presence or absence of fluid at the location of the sensor used some informative parameter, which value is then compared with threshold values. As specified parameter can be used directly the results of the measurements implemented in the detector in analog or digital form, or the value obtained in the processing of the measurement results with the help of some calculations. The result of the decision is issued in the form of the output logical signal "YES/NO". The output logic signal is generated, for example, a comparator that compares the magnitude of the informative parameter and the threshold value, and is supplied to any control device, for example on indicator.

Known thermal level switch for auth. the certificate of the USSR No. 1723449, G01F 23/22, publ. 30.03.1992, containing thermostability resistive bridge vkluchaysya permanent and one thermostability resistors, connected through a key element to a power source, and a differential amplifier, comparator and indicator light, indicating the presence or absence of liquid in a tank. The principle of operation of this device is based on measuring the difference of heat transfer coefficients in the liquid and gas termosaving resistor located at a manageable level. At lower liquid level below controlled, i.e. finding termosaving resistor in the gas medium, under the action of flowing current through it from the power source, the plug or turning off with the key element is alternately heating or cooling while reducing or increasing resistance, resulting in the indicator emits an intermittent signal. When exceeding the controlled level thermostability resistor is in a liquid, its temperature close to the temperature of the liquid, i.e. the temperature difference there, and the indicator light is off.

The main disadvantage of this method of determining the level and the implementing of the device is its relatively low performance due to the relatively large time required to warm up termosaving resistor to the temperature of operation Tmaxand the same time for cooling to Tminthat leads to snizeni the validity of the obtained information, and ultimately, reduce the reliability of the device and reduce the scope of its application.

Known thermistor detector liquid level by the RF patent №2217703, G01F 23/22, publ. 27.11.2003, containing casing, printed circuit Board with the measuring circuit, a source of DC power, located on the PCB, thermistor and display, and thermistor is electrically connected to the current source and the measuring circuit and is located outside the housing, and the remaining elements of the device inside it. In this device, thermistor is constantly in a hot state, which is its work operating condition. The fluid level control is carried out using a simple measuring circuit is an electronic relay, which operates in the mode of "Yes-no". The signalling device is prepared for operation (heated) air or gas. When the fluid in the control zone, i.e. in the immediate vicinity of the device, thermistor abruptly changes its resistance due to different coefficients of thermal conductivity of liquid and gas, resulting electronic relay closes and goes into a "Yes."

Known detector has a relatively simple electrical circuit, but only one termosaving element prevents it long without kazou work and obtaining reliable data in a wide range of temperature-controlled environment. In addition, this device and its operation modes are characterized by a low speed (about 15) due to the relatively large time to heat thermistor to the temperature of the working status and the same time on the fire. In addition, the scope of application of the device is very limited, because it can signal only on the presence of a certain liquid level, and does not reflect the presence of her move.

Closest to the technical nature of the claimed is thermal detector of the liquid level and the way his actions by the patent RF №2185603, G01F 23/24, publ. 20.07.2002, the level switch liquid level contains two series-connected thermistor installed in the level sensor placed in the vessel. When switched on, the device thermistors connected to a constant current source and have temperature coefficients of resistance (TCR) of the same sign, the same heat transfer coefficients, and their nominal resistance differ from each other. The detector also contains connected in series managed dip switch key, analog-to-digital Converter and the unit, the output of which is connected to the measuring input of the comparator, the reference input of which is connected to a source of reference signal, and the output is connected to perform the d device made in the form of indicator.

The method of operation of this device is based on the fact that, since the resistance value of one of the resistors is more (or less)than the second, with the passage of the current from the source and the heating temperature at them in a gas environment will be different, and the ratio of the resistances will be more (or less) a dimensionless coefficient K. on the other hand, when the sensor thermistors in a liquid the temperature of each of them will be almost equal to the temperature of the liquid, i.e. the ratio of the resistances of thermistors will be constant and equal to the coefficient K. Taking into account both of these conditions, the known device makes it possible to distinguish the presence of a liquid or gas in the place of installation of the sensor regardless of the absolute values of the temperatures of liquid and gas at a minimum temperature of thermistors relative to the ambient temperature.

However, the device and method of its action, like the previous, very low speed, that is, require a relatively long time (about 15-30 C) for the operation of the device, especially when going into the control zone from a liquid to a gas, due to the need for heating both of thermistors to the working temperature and the same time cool. The device also requires significant energopetrol is possible. All this leads to reduced efficiency and reliability of the detector and to limit the scope of its application.

In addition, the known device does not allow to obtain information about the movement (flow) are in the pipeline or reservoir fluid, which also reduces the possibility of its use.

The invention solves the problem of increasing the efficiency of determining the level and flow of liquid by increasing the speed of operation of the device, reduce energy costs and extend the scope of its application by monitoring not only the availability and level of liquid in the tank, but its move, especially when used in pipelines for various purposes.

To obtain a technical result according to the method based on the use of two thermistors having the same thermal characteristics, including heat one thermistor electric current and cooled by heat transfer to the environment, periodic measurement of the voltage drop across the resistors, the calculation of the informative parameter, comparing it with a threshold value and a decision about the presence or absence of fluid at a controllable level, periodically heated one of thermistors short pulses from the power source, after the end the of the heating repeatedly measure the ratio of the voltages is not heated and the heated thermistors, and as informative parameter that determines the level of the liquid, calculate the normalized time derivative by array processing measurement results of the specified relation.

The heating thermistor carried out with a period of no more than 2, and heating a thermistor in each period does not exceed 1, and the calculation of the normalized time derivative is carried out before the beginning of the next heating cycle. To determine the flow of liquid value of the normalized time derivative is additionally compared with the second threshold value, and then take a decision about the presence or absence of the fluid at a controllable level, the second threshold value exceeds the first.

A device for determining the liquid level, containing two thermistor installed in the sensitive element connected to a power source and having temperature coefficients of resistance (TCR) of the same sign and the same heat transfer coefficient in the gas, as well as analog-to-digital Converter and comparator, the reference input of which is connected to a source of reference signal, and the output is connected with an actuating device is further provided with a pulse switch, one contact of which is connected to the power source, and the other contact is connected to serialnum input analog-to-digital Converter, and connected in series with the regulator heat time, one input of which is connected to the output of analog-to-digital Converter, and the output connected to the control contact pulse switch, and a synchronizer, one output of which is connected to the third input of the regulator time of heating, as well as the evaluator of the normalized derivative, the output of which is connected with the second controller input time of heating and measuring input of the comparator, and the input connected to the output of the analog-to-digital Converter and the second output of the synchronizer. While the nominal resistance of thermistors of the same.

In addition, as the ballast resistance of the device is further provided with two resistors, connected one in series with each thermistor and forming together with the resistors resistive dividers, the midpoints of which are connected respectively to the measuring and reference inputs analog-to-digital Converter, one common point of a resistive divider connected to the power source and one contact pulse switch, and the other their common point connected to a common analog-digital Converter and grounded.

In the embodiment of the device impulse switch made in the form of series connected bipolar radio the investment of an electronic key and the ballast resistor, while the actuating device in the form of indicator.

In addition, to ensure the alarm about the presence of fluid flow, the device is further provided with a second comparator, connected in parallel to the first and the second execution unit, and the reference input of the second comparator is connected to the source of the other of the reference signal measurement input connected to the output of the transmitter of the normalized derivative, and the output is connected with the second actuating device. When this threshold voltage at the input of the second comparator is set greater than the threshold voltage at the input of the first comparator.

The invention consists in the fact that of the two thermistors, the working and reference, identical in terms of heat capacity and heat transfer in the environment, one (working) periodically heated for a very short period of time using pulse from the current source, and after heating control normalized speed reducing its temperature, which is set to a value that allows you to judge the heat transfer from thermistor in a controlled environment. When this normalized speed reduction of the working temperature (heated) thermistor is characterized by a function of the normalized derivative against the Oia voltage drops on the desktop and reference thermistors time.

After that, the value of the normalized derivative is compared with predetermined threshold values and decide according to the environment gas or liquid, and the presence of a moving fluid.

Normalized speed of decrease of the temperature determined at the beginning of the transition process, and then produce a new heating cycle thermistor and cooling, without waiting for them to cool to ambient temperature.

The duration of this series is about one second, which is about ten times shorter than the duration of thermal transients in a similar known structures. And since the speed reduction of the working temperature of thermistor is determined at the end of each period, the claimed technical solution provides very little time to establish the environment (gas or liquid).

The temperature difference between the working and reference thermistors proportional to the measured ratio of the voltage drops at the resistors at a known value of a flowing current.

The invention is illustrated by drawings, where figure 1 presents a functional diagram of the device for determining the level and flow of liquid; figure 2 shows time diagrams for the different States of the device; figure 3 - temperature dependence F and module its normalized derivative.

The device contains two identical thermistor 1 and 2 (taken for reference and a work Desk are respectively installed in the sensitive element 3 placed in the tank (level switch) or in pipeline (detector presence of liquid and its flow). In series with each thermistor 1 and 2 includes two resistors 4 and 5, respectively, used as ballast resistors.

thermistors 1 and 2 together with the resistors 4 and 5 form a resistive dividers, one common point which is connected to the power source 6, and the other their common point grounded. The resistance of the resistors 4 and 5 are similar in magnitude and much more nominal resistance of thermistors 1 and 2. In the embodiment, as ballast resistors can be enabled transistors or other electronic device that creates a lot of resistance in an electrical circuit.

thermistors 1 and 2 have the same nominal resistance, heat capacity and heat-transfer coefficients in the environment, structurally separated from the controlled environment of a thin wall of the sensing element 3, made for example of stainless steel foil, and placed in the same position in relation to the controlled fluid. The temperature coefficients of resistance (PTC) thermistors one is appropriate and can be both negative or positive. In a preferred variant implementation, the devices are thermistors with a negative temperature coefficient.

In parallel with the resistor 5 is connected impulse switch 7, one contact of which is connected to the power source 6 and the common point of the resistive divider, and the other contact is connected to the middle point of one of the resistive dividers, including work thermistor 2. Impulse switch 7 is made, for example, in the form of series-connected electronic key 8 and the ballast resistor 9 and is intended for short-term (pulse) power source 6 to the working thermistor 2. In the embodiment, as an electronic switch 7 can be used controlled pulse generator current that instead of the power source 6 is in the pulse mode to supply power to thermistor 2.

The midpoint of a resistive divider comprising thermistor 2, connected to the measuring input of the analog-to-digital Converter (ADC) 10, the midpoint of a resistive divider comprising thermistor 1, is connected with its input to connect the reference voltage, and a grounded common point of resistors 1 and 2 is connected to its corresponding common entrance. In addition, the ADC 10 is usually provided with a protective circuits input overload (the drawing is not shown).

The structure of the device also includes a digital control device 11, which includes the transmitter normalized derivative 12, the regulator heat time 13, the synchronizer 14 and comparator 15 and 16. In the embodiment of the device, which was pilot-tested, ADC 10, and all blocks of the control unit 11 is made on the basis of one chip (for example, type PIC12F6831/SN). In this case, all informative signals between the ADC 10, the control device 11 and its blocks are digital codes or binary logic signals.

The output signal of the analog-to-digital Converter 10 is supplied to one of inputs of the regulator heat time 13 and the input of the transmitter of the normalized derivative 12, the output of which, in turn, is connected with the second input of the regulator heat time 13, and also with the measuring inputs of the devices compare 15 and 16. On the reference input of the comparator 15 is set to the threshold voltage of P1, for example, from the reference signal 17, and the reference input of the comparator 16 to the threshold value P2, for example, from a source 18, and P2 is greater than P1. Because, as noted above, all blocks of the control unit 11 can be implemented in a single integrated circuit with embedded software, the reference voltage E1 and E2 can be specified and under the cha provided programmatically.

At the output of the comparator 15 is formed by a logical signal of "fluid", the output of comparator 16 is a logical signal the Presence of a flow of liquid, which is served on any of the actuators 19 and 20, such as an electronic switch that enables or disables the pump, or reflected on a light or sound indicator.

The synchronizer 14 is designed for cyclic (periodic) run time controller heating 13 that defines the duration of the enable pulse switch 7, and evaluator of the normalized derivative 12, which processes a sequence of output signals of the ADC 10 after the operation of the pulse switch 7. The outputs of the synchronizer 14 is connected with the control input of the transmitter of the normalized derivative 12 and the third input (input start) regulator heat time 13.

The method is as follows.

With a period of approximately one second on a small variable time (less than 0.5 seconds) of the control signal synchronizer 14 run time controller heating 13, an output pulse which closes the key 8. During this time through thermistor 2 runs additional current pulse from the source 6, which raises the temperature of thermistor 2 compared with the temperature of thermistor 1. The fact itself is m after opening the key 8 the temperature of thermistor 1 is always less than the temperature of thermistor 2. Since the nominal resistance and temperature coefficients of the resistors 1 and 2 are the same, for example negative, the resistance of thermistor 1 is greater than the resistance of thermistor 2, and therefore, the voltage drop across thermistor 1 is greater than thermistor 2.

The signals from the outputs of the resistive divider of resistors 1 and 2 are received at the reference and measuring inputs, respectively, of analog-to-digital Converter 10. This informative output signal (code) N ADC 10 is directly proportional to the voltage on the measuring input and inversely proportional to the voltage at the input of the reference voltage and the reference voltage is a normalizing value for the voltage on the measuring input.

As you know, the ADC converts the input voltage U in N (numeric code) according to the following rule: if the input voltage U is equal to the "reference" Uop, code N=Nmax. If U=0, code N=0. When code N is defined as the integer part of the value obtained from the expression:

That is, code N on the ADC output is linearly proportional to the input voltage, referred (normalized) to a "reference", which essentially sets the scale of the ADC. When the voltage at the reference thermistor, is equal to Uopaccordingly, the number on the ADC output is the measured value of the relationship of the voltage U on the desktop thermistor voltage on the reference thermistor. The measured value differs from the true on error sampling. This error is associated with its own characteristic ADC - Nmax: the larger Nmaxthe more precise the ADC. The most widely ADC with such values of Nmaxas 1023, 2047, 4095, 8195, 65535. In the claimed technical solution is possible the use of inexpensive ADC with Nmax=1023 unlike the prototype, which will require an ADC with Nmax=8195 or 65535.

As the resistance of the resistors 4 and 5 are similar in magnitude and much more nominal resistance R0thermistors 1 and 2, the ratio of the voltages at the resistors 1 and 2 is almost equal to the ratio of their resistances:

where R1t, R2tresistance 1-St and 2-nd thermistors when temperatures T1and T2;

T0- the temperature at which you set the nominal resistance of thermistor R0;

F(T-T0) is a dimensionless function, showing the dependence of the resistance of thermistors temperature, F(0)=1.

The output informational signal N analog-to-digital Converter 10 is also proportional to the ratio of the resistances of thermistors 1 and 2. In case of equal resistances of thermistors 1 and vyhodnoi informative signal of N analog-to-digital Converter 10 is equal to the maximum value of N max.

Directly after opening the key 8 the ratio of the resistances of thermistors 1 and 2 as much as the cooling of thermistor 2 against the resistance decreases and tends to unity. At the same time, the output signal of the analog-to-digital Converter 10 tries from the initial value N to the maximum value of Nmax.

Denote the difference in Nmaxand N as Δn As ΔN is much less than Nmaxthen taking into account formulas (1)to(4) will receive approximately:

The temperature difference T1and T2small (unit ° (C), respectively, and the ratio of the resistances of thermistors accurately expressed using the normalized first derivative of the temperature function F(T-T0), which we denote by DF(T-T0):

The ratio of the resistance can be approximated by the expression:

where ΔT=T2-T1- the temperature difference between thermistors.

From formulas (5) and (7) it follows that the largest ΔN, measured by the ADC 10, it is possible to judge the temperature difference ΔT thermistors 1 and 2:

The functional dependence F(T-T0), for example, thermistors NTC company EPCOS close to exponential, so formirovaniya the first derivative is barely changed in a wide range of temperatures. The divisor Nmax× DF(T2-T0in the formula (8) remains almost constant, therefore, ΔN is directly proportional to the temperature difference ΔT thermistors 1 and 2.

After heating the temperature difference ΔT thermistors 1 and 2, and the difference ΔN tend to zero at a speed determined by the heat transfer to thermistor 2 in the environment. Due to the identity of thermal characteristics of thermistors 1 and 2, the rate of change of the temperature difference ΔT is also determined primarily by heat transfer from thermistor 2 in a controlled environment and is virtually unaffected by changes in its temperature. Estimates of the rate of cooling of thermistor 2 after heating is performed by the evaluator of the normalized derivative 12. The output signal P of the transmitter 12 is defined as the estimate derived from the difference ΔN during the time the temperature of thermistor 2, normalized by the average value of the ΔN at the same time.

In particular, the evaluation of the derivative of the difference ΔN can be performed by the method of least squares. In this case, the output signal P of the transmitter 12 is determined by the formula

where m is the number of output signals of the ADC 10, recorded and processed by the evaluator of the normalized derivative 12 after the end of the slave whom you pulse switch 7 in the process of cooling the working thermistor; in the particular case, for example, m=15;

ΔNi - separate measurement result ΔN i;

Σ - summation is from i=0 to i=m-1.

The advantages of using the normalized time derivative as an informative parameter used in the proposed method, unlike the prototype, where as an informative parameter is the ratio of the resistances of the two thermistors, heated the same amount of constant current can be explained by the graph in figure 3, which shows temperature dependence of the function F and the module its normalized derivative DF for typical thermistors with a nonlinear characteristic and a negative temperature coefficient (for example, firms HEROS) in a fairly typical range of temperatures from 5 to 55°C. As can be seen from the data, the function decreases from the value of 2.5 at a temperature of 5°With up to 0.17 at a temperature of 55°C, i.e. in the specified temperature range varies approximately 15 times. Its normalized derivative varies by only 23%from - 0.22 to - 0.17.

Figure 2 presents the timing diagram for different situations:

phase 1 corresponds to the presence of the sensing element 3 in the air;

- during phase 2 is slow filling of a controlled volume of liquid;

- with the beginning f the PS 3, the liquid moves at a speed of not less than 0.1 m/h, for example, when the pump;

- with the beginning of phase 4, the liquid disappears from the monitored volume, but the surface of the sensing element while still moistened;

- phase 5 corresponds to the finding of the sensing element 2 in the air.

In phase 1 the modulus of the normalized derivative of P at the output of the transmitter 12 does not exceed the threshold P1, respectively, the logical signal "fluid" at the output of the comparator 15 and respectively at the input of the Executive device (indicator) 19 equal to zero, which means the absence of a liquid in a controlled volume. During phase 2, the speed reduction of the temperature difference ΔT after the end of heating increases. At the end of phase 2 module of the normalized derivative of P increases. Since the modulus of the derivative of P in this case exceeds the threshold P1, the logical signal corresponding to the presence of fluid at the output of the comparator 15 receives a single value and, accordingly, the indicator 19 reflects the status of the "fluid". It should be noted that the appearance of a signal of the presence of fluid behind one period (1 second) from the actual appearance of the liquid in a controlled amount.

When liquid flows in a controlled amount with sufficient speed (phase 3) cooling of thermistor 2 is not only due to the convection in the liquid is, but due to the effective heat transfer associated with its movement. In this case, the rate of decrease of temperature difference ΔT after heating becomes almost maximum and is determined primarily by the design of the sensing element 3. Module derived P in the fluid flow exceeds a threshold P2, Boolean signal the Presence of a flow of liquid at the output of the comparator 16 and respectively at the input of the indicator 20 will take a single value. Moments of transition specified logic signal "unit" and "zero" is also off by one period of the heating cycle from the actual appearance and loss of flow of liquid in a controlled amount.

Phase 4 figure 2 illustrates the case of a sudden loss of fluid from the controlled volume, for example, due to the fact that ended the liquid in the tank from which it was pumped. In a controlled volume remains small amount of liquid, which slowly drains from the surface of the sensing element, which may be related, in particular, with the presence of foam. As a logical signal the Presence of a flow of liquid within 1 second will be equal to "zero", it can be effectively used, for example, for emergency shutdown of the pump. Logical signal of "fluid" go to "zero" with some delay (phase 5), is which is the greater, the higher the viscosity of the liquid.

For each phase of the above process controller the heating time 13 set its value to the duration of the output pulse, which controls the circuit of the electronic key 8. Almost the regulation time of heating carried out in such a way that with the increase of the normalized derivative of P, and hence heat losses of the working thermistor, increasing heating time. Conversely, when the decrease of the normalized derivative of the input to the controller 13 from the output of the transmitter 12, reduced heating time. This allows you to have approximately the same average temperature of the working thermistor above the support (approximately 4÷8°).

Thus, compared with the prototype using the claimed invention allows to provide significantly better performance of the device for measuring fluid (about 7-10 times) during the transition of its sensitive element from a liquid to a gas and just better performance (about 3-5 times) in the transition from gas to liquid, and also to reduce the cost of electricity to heat thermistor, which allows to increase the efficiency of the device as a whole. In addition, the invention allows to extend the field of use of the device for determining the liquid level is and the possibility of controlling not only the presence of liquid, but its duct, which is especially important when using the device in pipelines for various purposes.

1. The method for determining the liquid level based on the use of two thermistors having the same thermal characteristics, including heating of thermistor electric current and cooled by heat transfer to the environment, periodic measurement of the voltage drop across the resistors, the calculation of the informative parameter, comparing it with a threshold value and a decision about the presence or absence of fluid at a controllable level, wherein the periodically heated one of thermistors short pulses from the power source, after heating repeatedly measure the ratio of the voltages of unheated and heated thermistors, as well as informative parameter that determines the level of the liquid, calculate the normalized time derivative by processing the array of the measurement results of the specified relation.

2. The method according to claim 1, characterized in that the heating of thermistor carried out with a period of no more than 2 C.

3. The method according to claim 1, characterized in that the heating time of thermistor in each period does not exceed 1 C.

4. The method according to claim 1, characterized in that the calculation of the normalized time derivative exercise PE the units by the beginning of the next heating cycle.

5. The method according to claim 1, characterized in that for determining the flow of liquid value of the normalized time derivative is additionally compared with the second threshold value, and then take a decision about the presence or absence of the fluid at a controllable level.

6. The method according to claim 5, characterized in that the second threshold value exceeds the first.

7. A device for determining the liquid level, containing two thermistor installed in the sensitive element connected to a power source and having temperature coefficients of resistance (TCR) of the same sign and the same heat transfer coefficient in the gas, as well as analog-to-digital Converter and comparator, the reference input of which is connected to a source of reference signal, and the output is connected with an actuating device, characterized in that it is further provided with a pulse switch, one contact of which is connected to the power source, and the other contact is connected to the output of the working thermistor and measuring input analog-to-digital Converter, and connected in series regulator heat time, one input of which is connected to the output of analog-to-digital Converter, and the output connected to the control contact pulse switch, and a synchronizer, one output of which is outinen with the third controller input time of heating, as well as the evaluator of the normalized derivative, the output of which is connected with the second controller input time of heating and measuring input of the comparator, and the input connected to the output of the analog-to-digital Converter and the second output of the synchronizer.

8. The device according to claim 7, characterized in that it is further provided with two resistors, connected one in series with each thermistor and forming together with the resistors resistive dividers, the midpoints of which are connected respectively to the measuring and reference inputs analog-to-digital Converter, one common point of a resistive divider connected to the power source and one contact, pulse switch, and the other their common point connected to a common analog-digital Converter and grounded.

9. The device according to claim 7, characterized in that the nominal resistance of thermistors of the same.

10. The device according to claim 7, characterized in that the impulse switch is made in the form of series connected bistable electronic switch and the ballast resistor.

11. The device according to claim 7, characterized in that the actuating device is designed as a indicator.

12. The device according to claim 7, characterized in that to indicate the presence of a flow of liquid, the device updat is further provided with a second comparator, connected in parallel to the first and the second execution unit, and the reference input of the second device is connected to the source of the other of the reference signal measurement input connected to the output of the transmitter of the normalized derivative, and the output is connected with the second actuating device.

13. The device according to item 12, characterized in that the threshold voltage at the input of the second comparator is set greater than the threshold voltage at the input of the first comparator.



 

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1 dwg

FIELD: measuring engineering.

SUBSTANCE: device comprises fuel level indicator and rheostat pickup made of an analogue-digital converter with the balance input. The three-position switch is connected with the lever indicator. The device additionally has three resistive dividers, voltage stabilizer, and shunting resistor made of a 0.003-0.006-Om resistor. The rheostat level pickup is mounted inside the fuel tank vertically, and its linear horizontal size at this level is directly proportional to the area of the tank section in the horizontal plane at this level.

EFFECT: expanded functional capabilities.

1 dwg

The invention relates to the measuring of the level of the melt and can be used in the metallurgical industry, in particular in installations engaged in the welding of the metal surface layer on a cylindrical part

The invention relates to the field of measurement technology, in particular to the manufacture of devices level control of conductive liquid and bulk materials

The invention relates to the making, in particular to the means of control and measuring the level of liquid and granular media in confined spaces

Transmitter // 2204807
The invention relates to a device for measuring liquid level in open reservoirs, canals, sewage reservoirs and other hydraulic structures

FIELD: measuring engineering.

SUBSTANCE: device comprises fuel level indicator and rheostat pickup made of an analogue-digital converter with the balance input. The three-position switch is connected with the lever indicator. The device additionally has three resistive dividers, voltage stabilizer, and shunting resistor made of a 0.003-0.006-Om resistor. The rheostat level pickup is mounted inside the fuel tank vertically, and its linear horizontal size at this level is directly proportional to the area of the tank section in the horizontal plane at this level.

EFFECT: expanded functional capabilities.

1 dwg

FIELD: measuring engineering.

SUBSTANCE: method comprises pressing unit reinforced by electrodes with simultaneous forming of insulator between the electrodes. The space that is defined by surfaces of the electrodes is filled with casting plastic mass. The pressure tightness is provided by tightening the insulator with electrodes by means of a nut.

EFFECT: enhanced reliability.

1 dwg

FIELD: the invention refers to measuring technique and may be used for controlling bulk and liquid materials.

SUBSTANCE: the oscillating indicator of a level has a sensible element( a probe) 1 connected with an anchor 2, a driving arrangement 4 in the shape of a coil with a ferromagnetic core and also a sensor 5 of the displacements of the anchor, a drive-pulse generator 6 and an amplifier 7 and a relay block 9 successively connected. The amplifier is spanned with a regulated negative feedback fulfilled in the shape of a resistor 8. The sensor 5 of the displacements of the anchor may be fulfilled in the shape of a coil with a ferromagnetic core. At that the section of the anchor 2 between the coils is fulfilled out of non-magnetic material that prevents electromagnetic connection between the coils providing protection from high frequency oscillations in the system anchor-coil-amplifier.

EFFECT: allows to control the levels of the bulk and liquid materials being present in aggressive mediums, under pressure,( discharge)and at temperature till 200 degrees.

2 dwg

Level meter sensor // 2276333

FIELD: instrument engineering.

SUBSTANCE: level meter sensor comprises hollow rigid base with the port in its bottom end, diaphragm, strain gage converter with box, flexible spacer arranged over periphery of the box, and tube whose one end is mounted pressure-tightly in the port of the support and the other end is connected to the space of the box. The diaphragm is made of a rigid material and mounted on the flexible spacer for permitting cooperation with the strain gage converter.

EFFECT: enhanced reliability and simplified structure.

1 dwg

FIELD: the invention refers to the field of instrument making and designed for control of the level of dielectric and current conducting liquids in hydraulic systems (fuel, freezing, accumulative etc) for example the level of oil or cooling agent in transport vehicles.

SUBSTANCE: the liquid level meter has a two-electrode capacitance sensor with an external 10 and interior 11 electrodes electrically connected with an electronic scheme having a stabilized source of power supply, an amplifier, a generator and a trigger. According to the first variant the capacitance sensor is fulfilled in the shape of a coaxial condenser "C". The interior electrode 11 of the sensor is fulfilled tubular and is mounted inside a fluoroplastic probing rod 12. The interior electrode 11 is connected to the input of a phase comparator which is additionally introduced in the scheme and whose output is connected with input of the trigger and the output of the last is provided with a line of delay and has two outputs - direct and inverse connected with a transistor key fulfilled with possibility of fulfillment of an operation "switched on" or "switched off". At that the electronic scheme is fulfilled on a digital integrated microchip. According to the second variant the interior electrode 11 of the coaxial condenser "C" is fulfilled tubular and is additionally provided with a protective shield 22. The shield 22 is fulfilled in the shape of a spiral spring out of bronze and electrically connected with the external electrode - the body 10 of the coaxial condenser "C".

EFFECT: increases sensitiveness and accuracy of measuring of the level of liquid.

6 cl, 4 dwg

FIELD: invention refers to control-measuring technique and is assigned for control and signaling about border of interface between mediums petroleum product-water in installations for purification water from petroleum products or watered petroleum products from water.

SUBSTANCE: sensor has flange, three electrodes with sleeves on their low ends filled with fresh water, moreover two of them are covered with dielectric insulation. Electrodes with sleeves are located inside tube of protective screen and are fastened in flange with aid of stuffing boxes-insulators. Screen in upper part has diaphragm ring with openings along circumference coinciding with openings in screen forming swinging compensator and is fastened to flange with aid of screws. Electrodes of sensor together with sleeves and electronic part form oscillating contour going in resonance at presence in space between electrodes of electric conductive medium (water) with following triggering of executive elements and at presence of water between electrodes of petroleum product resonance of contour stops.

EFFECT: increases reliability of work of sensor.

2 cl, 1 dwg

FIELD: physics, measurement.

SUBSTANCE: invention is related to the field of facilities for automation of different liquids level detection in industrial and household reservoirs, and also for detection of liquids availability and flow in pipelines. Method is based on application of two thermistors that have identical thermal characteristics, and includes heating of one of the thermistors by electric current and its cool-down due to heat transfer to environment, periodic measurement of voltage drop at thermistors, calculation of informative parameter, its comparison with threshold value and making decision on availability or unavailability of liquid at controlled level. At that one of thermistors is periodically heated by short pulses from power supply source. After heating is completed, ratio of non-heated and heated thermistors' voltages are repeatedly measured, and as informative parameter scaled time derivative is calculated by means of specified ratio measurement results array processing. Device for method implementation contains two thermoresistors, which are installed in sensitive element, connected to power supply source and which have temperature resistance coefficients (TRC) of the same sign and identical coefficient of heat emission in gas. Besides, it also contains analog-digital transducer and comparator, reference inlet of which is connected to source of reference signal, and outlet is connected with actuating device. Moreover, device is equipped with pulse switch and serially connected regulator of heating time and synchroniser, and also calculator of scaled derivative. For alarm on liquid flow availability, device is additionally equipped with the second comparator that is connected parallel to the first one, and the second actuating device.

EFFECT: higher efficiency of liquid level detection by increase of device actuation fast-action, reduction of power inputs and expansion of its application field.

13 cl, 3 dwg

FIELD: measuring technology.

SUBSTANCE: invention refers to a measuring device for determination of an amount d(V(z)) of conducting liquid of the conductivity LF by a capacity with vertically (z-direction) varied filling points. There is provided conductivity metre which among others has at least two electrodes extended in a z-direction. The capacitance parametres and/or the metres are ensured so that it/they can be described by means of at least one parametric function, fpi (V(z)) depending on V(z). At least one said parametric functions shall have exponential dependence on V(z). There is also described measuring element, and also method for determination of total amount of flowing liquid d (V).

EFFECT: simplified design of the device and method of measuring conductivity of the conducting liquid.

42 cl, 14 dwg

FIELD: physics.

SUBSTANCE: method if based on measuring capacitance of a double-electrode capacitive liquid level sensor, which in turn in any sequence measures capacitance of the double-electrode capacitive liquid level sensor and capacitance of the same sensor is measured after connecting a capacitive sensor of dielectric properties to it, after which the level h from the upper end of the double-electrode capacitive liquid level sensor is calculated using the formula:

, where h is the level of the liquid in the reservior; CA is capacitance of the double-electrode capacitive liquid level sensor; CB is overall capacitance of the double-electrode capacitive liquid level sensor connected in parallel to the capacitive sensor of dielectric properties; A, B and D are structural parametres of the double-electrode capacitive liquid level sensor and capacitive sensor of dielectric properties. The device for measuring liquid level has a double-electrode capacitive liquid level sensor made in form of a coaxial capacitor, and two cylindrical electrodes. The lower end of the inner electrode of the double-electrode capacitive liquid level sensor is connected to one of the electrodes of the capacitive sensor of dielectric properties through the closing contact of a reed relay, and the lower end of the outer electrode of the double-electrode liquid level sensor is connected to the second electrode of the capacitive sensor of dielectric properties.

EFFECT: high accuracy of measuring the level of different liquids, as well as elimination of measurement errors caused by change in dielectric permittivity of the measured liquid.

2 cl, 1 dwg

FIELD: physics.

SUBSTANCE: sensor for monitoring the level of a liquid has a housing and a printed-circuit board on which there is a substrate having one or two identical film resistors (thermistors) and contact pads (conductors). The printed-circuit board is in form of a plate, one short side of which is rigidly attached to the base of the housing and on the edge of the opposite free side there is a hole whose diameter is 2…4 times larger than the width of the substrate lying over the hole and made from thin heat-insulating material. Each film resistor (thermistor) is in 'point' form with dimensions in the range (0.15…0.5) mm • (0.5…0.5) mm and thickness not more than 0.0005 mm. The boundary surface between each film resistor (thermistor) and contact pads of the substrate (conductors) is in form of broken lines consisting of straight sections.

EFFECT: high mechanical strength of the structure.

3 dwg

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