DE3337690C2 - - Google Patents

Description

The invention relates to a method and an apparatus for measuring the level in a container using sonic / ultra sound waves, whereby the time between the transmission of the sound / Ultrasonic waves and the reception of on the surface of the good sound / ultrasonic echo waves reflected the fill in the container standing height is determined.

When using sound / ultrasonic pulses to fill the level Measurements occur next to those from the surface of the goods in the container reflected echo signals suitable for the measurement often interference echoes, from which the correct echo signal can be distinguished got to. Such false echoes can be caused by struts or edges in the Containers are caused. To suppress false echoes the sound / ultrasonic waves are often tightly bundled and so out judges that their way on such edges or struts passed. Tightly bundled sound / ultrasonic waves can be only generate and hide the at a relatively high cost Disadvantage in itself because of the small diameter of the radiation cull the baffle ready to receive after reflection on the contents no longer to meet.

Another way to suppress false echoes is in the setting of a so-called "concurrent time window" or in the close range by distance-dependent gain change. Under one of the like time window is the limit for the level measurement solution of sound / ultrasound echo signals to be evaluated at one time  to understand space, which shortly before the presumed arrival of the Surface of the good reflecting echoes begins and shortly after suspected arrival ends. The "concurrent time window" changes to previously determined and valid sound / ultrasonic echo signal set. This method can be used to eliminate many interferences eliminate rivers. Arranged in the way of sound / ultrasonic waves disruptive parts that are initially covered by the contents and during the Sinking of the filling material is exposed and therefore by the sound / ultra sound waves are only detected as defects, if the amplitudes of the reflected sound / ultrasonic waves significantly larger than the amplitudes of the surface of the good are reflected sound / ultrasonic waves. If this is the case, then rest the "moving time window" to that of such a part, for example, an edge or a strut in the container Sonic / ultrasonic echo signal and only then delivers a correct one Level measurement if the level of the level with the height of this part in the container matches.

DE-OS 24 33 133 describes in general the use of Ultrasonic pulses for measuring fill levels. The one described there The device has, among other things, a transmitter converter, the electrical one Converts signals into ultrasound signals, a receiving transducer that Converts ultrasonic signals into electrical signals and a Amplifier circuit for the received echo pulses.

DE-AS 28 17 247 describes an arrangement for measuring distances through echo sounding. Reference echoes are used to calibrate the system, that result from a specified reference path. To receive the Reference echoes and the measurement echoes become the same electroacoustic transducer used. The reference value is not suppressed during the measurement, but rather in the form of a quotient for the relationship between the Runtime used in the reference path and that in the measurement path.

The invention is based, a method and a task to further develop the direction of the genus described at the beginning,  that the falsification of the measurement result by fixed parts of the Container that are in the way of sound / ultrasonic waves or protrude into the path, is eliminated.

This object is achieved by those described in claim 1 Measures solved. With the measures specified in claim 1 can Disturbing echoes can be easily distinguished from useful echoes. It is even possible to get multiple false echoes from one another in the path of the Acoustic / ultrasonic waves arranged parts are generated and block for further processing. If the waiter surface of the good is at the level of one of the parts producing false echoes, will the  Level measured correctly anyway. An increase in the surface surface beyond such a part or a sinking of the surface under the part is with the method specified in claim 1 recognized immediately in the measuring phase.

In an expedient embodiment, for in the way Sound / ultrasound signals arranged at given intervals knowledge or faults during the commissioning phase Times - or the amplitudes along with the running times of the sound / ultra sound waves measured and available for the operating phase saves. This will not only make it quick and easy Adaptation of the measuring method to the circumstances of the respective Measurement object possible, but only the prerequisite for measurement processing without refusal created.

In a further embodiment, multiple echoes in the course of the Commissioning recorded and taken into account when processing measured values does. As a result, such multiple echoes, for example at domed container bottom higher amplitudes than that of the useful echo have, from processing to a level indicator be kept away.

An expedient embodiment is that for Multiple echoes reflected between the bottom and ceiling of the container the running time is measured and a time diaphragm is set which is something is shorter than their term. With this measure, the Requirements for the suppression of the influence of the multiple echoes on the measurement result at the respective location quickly and be created in a simple manner.

A device for performing the described in claim 1 benen method according to the invention is that an electri  signal into sound or ultrasound signals and received Converting sound or ultrasonic signals into electrical signals Converters each with a high-frequency transmitter and a reception amplifier is connected and that the radio frequency transmitter and the Receiving amplifiers are connected to a microcomputer which is connected to a non-volatile read-write memory, in the input elements connected to the microcomputer Data on the duration of false echoes or the altitude of Obstacles or imperfections can be entered. This just opened up built device has a non-volatile memory in which the setting values for the respective measurement object also after Switch off the power supply. For the measurement direction is therefore not a constant operating voltage required. Only at the beginning of a level measurement the operating voltage is switched on.

A is expediently in the non-volatile program memory Control program for the microcomputer included, which according to the This control program commands the transmitter to deliver a high-frequency pulse train. With the microcomputer who according to the instructions of the control program the transmission of the sound / ultrasonic waves by adding them up of clock pulses the transit times of the ultrasonic sound waves at Received the sound / ultrasonic echo waves fixed. The Mikrocom puter is u. a. one to the output of the receive amplifier connected analog-digital converter downstream, the just if in accordance with the control program with control signals is applied.

In a preferred embodiment it is provided that the Microcomputer a range indicator assembly and a multipli decorative digital-to-analog converter is connected. With this type  order is the influence of temperature changes on the barrel time of the sound / ultrasound runtime medium via a variable Gain setting balanced. The measurement result of the Ge advice is therefore independent of the temperature of the specific Sound transit time.

An expedient embodiment is that an input element is designed as a button, when pressed the Measured value of the transit time of the multiple reflected from the container bottom echoes taking into account a small security value by means of of a programming cycle can be entered into the non-volatile memory is. The term minus the security value is determined by the Control program in a specially reserved storage space entered. No knowledge of the tax pro is required for the entry grams necessary. All you have to do is press the button if multiple echoes have arisen on the bottom of the container using the pre direction on the range indicator assembly.

In another preferred embodiment is an input element ment formed as a button, when pressed, the measured values the runtime of one generated by an obstacle or a defect th sonic / ultrasonic interference echoes and the associated amplitudes of the Sound / ultrasonic echo waves by means of a programming cycle in the volatile memory can be entered. The run just found time along with the associated amplitude of the received sound / ultra Sound echo signals are switched off when this button is pressed selected memory locations of the non-volatile memory. The Storage spaces are defined in the control program. The Adjustment of the device to the existing obstacles or Impurities do not require knowledge of the internal structure of the device device or the control program.

Further advantageous refinements of the inventive concept are described in claims 2, 7, 10 and 11.

The invention is described below with reference to a drawing illustrated embodiment explained in detail, from which further features and advantages result.

In the drawing, a device for measuring the level in a container by means of sound / ultrasonic waves is shown. The sound / ultrasonic waves are generated with a sound converter 10 , which converts the high-frequency electrical signals supplied to them, the frequencies of which are in the sound / ultrasonic wave range, into sound / ultrasonic waves or ultrasonic pulse packets, and emits them. The sound transducer 10 is arranged in a container, not shown. The alignment of the baffle lers 10 enables the continuous determination of the level of the goods in the container from the bottom to a limit lying close to the upper end of the container. Obstacles, e.g. B. struts or other fixed container parts, may be arranged. During the pauses between the transmission of ultrasonic wave pulse packets, the transducer receives 10 sound / ultrasonic echo waves from the reflecting surface and converts them into corresponding electrical signals. The output of a high-frequency transmitter 12 is connected to the sound converter 10 and generates high-frequency pulse packets when it is excited via an input (not specified in more detail) by a control signal emitted by a microcomputer 14 .

At the transducer 10 , the input of a receiving amplifier 16 is still connected, the gain element is adjustable. For this purpose, the amplifier 16 has a control input 17 . The output of the receive amplifier 16 is connected to an input 18 of the microcomputer 14 . The input 18 is followed by an analog-digital converter, not shown, which is expediently part of the microcomputer 14 .

The microcomputer 14 is connected via bidirectional lines 20 to a non-volatile memory 22 in which a control program is stored.

Data outputs 24, 26 of the microcomputer 14 are each a multiplying digital-to-analog converter 28 , hereinafter referred to as D / A converter, and a distance indicator module 30 is switched on. The distance display module shows, for example, digitally in centimeters when a sound / ultrasound echo signal is received, the distance between the sound transducer 10 and the point at which the sound / ultrasound signal was reflected. The output of the D / A converter 28 is connected on the one hand to the control input 17 of the receiver 16 and on the other hand to a switching element 32 which can be controlled by the microcomputer 14 . With the switching element 32 , an analog signal current memory 34 is connected, which contains an output 36 , to which a remote evaluation device, not shown, is connected.

The D / A converter 28 contains a control input 29 , to which a (for example arranged in the container) temperature sensor 38 is connected. The components 10, 12, 14, 16, 22, 28, 30, 32 and 34 who supplies the operating current from a power supply device 40 . The power supply device 40 , the z. B. generates a regulated te output voltage, device 42 is supplied with energy from the evaluation device.

Three buttons 44, 46, 48 are connected to control inputs of the microcomputer 14 , not shown in any more detail. The buttons 44 to 48 trigger in connection with the control program contained in the memory 22 certain functions of the device shown in the drawing Darge. The reflected sound / ultrasonic echo signals received by the sound transducer 10 pass through the receiver 16 into the microcomputer 14 and are stored in a memory, not shown, with random access. The stored data is represented by the display module 30 via, for example, an LED display. In the microcomputer 14 , the time period between the transmission of a sound / ultrasound pulse or a sound / ultrasound pulse packet and the reception of a corresponding sound / ultrasound echo signal is measured and also shown on the display module 30 . Information proportional to the measured period of time from the position between the sound transducer 10 and the reflecting surface is output by the microcomputer 14 to the D / A converter 28 . The measurement of the time difference, which is the transit time of the sound / ultrasonic waves from the transducer 10 to a surface reflecting the waves and from this surface back to the transducer 10 , is carried out in the microcomputer 14 by counting high-frequency clock pulses, the frequency of which, for. B. is rich in megahertzbe.

From the transit time, the distance between the transducer 10 and the respective reflecting surface is determined in the microcomputer 14 by means of the control program in the memory 22 , which contains the value for the specific speed of sound of the transit time medium, and z. B. shown on the range indicator assembly 30 . The level is preferably determined on the basis of this distance, which is the difference between the distance between the filling material and the sound transducer and the height of the sound transducer 10 above the bottom of the container. Appropriately, the level determined in this way can also be shown on the display module 30 and output to the D / A converter 28 .

When the button 44 is pressed, the values of the sound / ultrasonic echo amplitude and the fill level shown on the display assembly group 30 are transferred to the memory 22 . A programming cycle is triggered for this. The control program reserves its own memory locations for this data.

When the button 46 is actuated, the fill level shown on the display module is transferred into the memory 22 , taking into account a safety distance. A programming cycle for the memory 22 is also carried out for this purpose. The incoming via the push button 46 , modified by the safety distance measured value is used with the help of the control program to generate a time diaphragm, which sets a time limit, when exceeded, the still received sound / ultrasound echo signals are not processed. In this way, the reflected multiple echoes, the amplitudes of which can be higher than those of the useful echo generated by the product surface, can be kept away from the level indication.

Both the useful echo waves and the false echo waves, which emanate from obstacles in the path of the transmitted sound / ultrasonic waves, are received by the sound converter 10 . The altitude and the amplitudes of the interference echo waves generated by the obstacles remain the same and are recorded in advance and contained in the non-volatile memory 22 . In the measuring mode of the device, who received the sound / ultrasonic echo waves compared with the data stored for interference echo waves. If there is agreement between the received and the stored values within predefined tolerance limits, then the received sound / ultrasonic echo waves are recognized as false echo waves and are not processed further for the fill level indication. If the amplitudes and the height information of the received sound / ultrasonic echo waves lie outside the stored values, then it is a question of the echo waves reflected from the surface of the material in the container, which are output as the fill level after appropriate conversion by the switching element 32 is controlled via the microcomputer 14 . A value corresponding to the fill level thus reaches the distance display module 30 via the analog memory 34 .

If no sound / ultrasonic echo waves are received, their Amplitude and height is outside the stored values, then is this a sign that the product is one of the Obstacles. To fill the level for this case average, the amplitudes of the level of the obstacles are reflected evaluated sound / ultrasonic echo signals. Are saved the amplitudes of false echoes that result when the contents surface is not exactly at the level of an obstacle. Not the amplitudes that are covered by the product are stored obstacle. The latter amplitudes can vary depending on Absorbance of the good in the container, be very low.

It is possible to store the transit times of the sound / ultrasound interference echo signals or the calculated heights of the obstacles above the tank bottom and to compare them in the measuring mode with the sound / ultrasound echo signals received. The gain of the receive amplifier 16 is controlled in dependence on the D / A converter output signal. About the temperature sensor 38 , the output signal of the D / A converter 28 is controlled so that it is not influenced by a corresponding influence on the D / A converter 28 from temperature changes in the transit time medium in the container.

When the device shown in the drawing is started up, the distance actually measured or the distance of the false echo appears in centimeters, for example, on the internal LCD display 30 of the device. This makes it possible to determine whether a false echo is present or whether the true fill level is displayed. The height of the obstacles above the ground is assumed to be known.

If there is a source of interference within the measuring section, the distance displayed does not match the distance of the true level. By pressing the assigned key 44, which corresponds to the meaning "distance too small", the amplitude and the distance can be stored for an existing false echo. The same storage procedure can then be carried out with a possible further false echo. The storage process described can be repeated several times, ie several false echoes can be stored.

But it also happens that an "multiple echo" is greater in amplitude than the useful echo when the container is empty. This indicates that the distance is too great. By actuating the further key 46 , which corresponds to "distance too large", the maximum measuring range can be limited in such a way that its time equivalent is shorter than the time of the multiple echo to be masked out. Analogous to the above, the characteristics of the multiple echo are transferred back to a non-volatile memory.

The method described above can also do this can be used, in advance known defects through verified Eliminate switch or button setting.

In the course of commissioning, the above-described device initially interprets a false echo as a product echo. An operator can recognize the presence of a false echo from the LCD distance display. By actuating the button 44 "distance too small" all data of this echo are stored under the pseudo name "false echo 1".

At the same time, a new search cycle will start from the end of this echo initiated to the end of the measuring range, and the echo found displayed. During the subsequent filling, the defect becomes or the obstacle is covered by the product. To prevent, that in this case the product is declared as false echo,  the measurement processing of the device ensures that the disturbance echo interpretation is switched off before the contents of the fault exceeds.

Conversely, the device evaluates when emptying the container an outgoing echo as a false echo as soon as the true product echo exceeds the distance for a False echo has been reserved. That means in the case of larger distances the device evaluates this for the product as that for the false echo shorter echo than false echo and longer in time than the real one Level. If the filling material is at the level of the fault point, so the device continuously searches beyond the distance to the fault location going after another echo that has a smaller amplitude than that can have false echo. Thus, even with a lower amplitude of the product echo is recognized as that of the false echo when the product stood larger distances than the distance to the false echo. Multiple echoes are suppressed in this search cycle. It ver serves to emphasize that the measures mentioned find the true level echoes regardless of the tank filling ensure every time the device is switched on.

The button 48 is used to select a specific operating mode of the microcomputer 14 . When the button 48 is actuated, two measured values are recorded for the surface of the material in the container. The measured values correspond to the highest and the lowest point of the surface. The mean level is determined by averaging these two measured values.

Claims (13)

1. A method for measuring the filling level in a container by means of sonic / ultrasonic waves, wherein the filling level is determined by the time between the transmission of the acoustic / ultrasonic waves and reception of reflected at the surface of the material in the container acoustic / ultrasonic wave, characterized characterized in that sound / ultrasonic waves, which are generated by obstacles or imperfections arranged between the fill level surface and the sound transducer ( 10 ), are determined at their previously recorded and stored running time or at the previously recorded and predetermined height above the tank bottom and not for the level indicator will be processed as soon as a sound / ultrasound echo signal that is not assigned to an obstacle or a fault location is received, so that only waves whose transit time is outside the previously determined transit time of the obstacles are processed for the level indicator, and that if none is missing the last received acoustic / ultrasonic echo wave from the series of acoustic / ultrasonic echo waves, which are generated by obstacles or imperfections that are not covered by an object, is further processed for the level indicator. 2. The method according to claim 1, characterized, that in the absence of an obstacle or one Impairment assigned to the sound / ultrasound echo wave for the last fault location not covered by the good or the last one not obstacle covered by the well, performed a measuring operation with which, going beyond the interference echo waves assigned runtime or altitude limits, sound / ultrasound echo waves are determined, the amplitudes of which can be predetermined Values are less than the amplitudes of the interference echo waves and which are processed for the level indicator. 3. The method according to claim 1 or 2, characterized, that sound / ultrasound echo through a predeterminable time window waves reflected from the bottom of the empty container, be hidden. 4. Procedure according to one of the An sayings 1 to 3, characterized, that for given in the path of sound / ultrasonic waves Distances arranged obstacles or impurities in the Set-up phase the amplitudes and the running times of the sound / Ultrasonic echo waves measured and available for the measurement phase get saved. 5. The method according to claim 3, characterized, that in the adjustment phase for that from the bottom of the container reflected sound / ultrasonic echo waves measured the transit time and set a time aperture that is slightly shorter than that Term is.   6. Device for performing the method according to one of claims 1 to 5 with a sound transducer ( 10 ) which converts electrical signals into sound / ultrasound signals and received sound / ultrasound echo signals into electrical signals and each with a high-frequency transmitter ( 12 ) and one Receiving amplifier ( 16 ) is connected, characterized in that the high-frequency transmitter ( 12 ) and the receiving amplifier ( 16 ) are connected to a microcomputer ( 14 ) which is connected to a non-volatile read-write memory ( 22 ), in which means input elements ( 44, 46, 48 ) connected to the microcomputer ( 14 ), data about the transit times of false echoes or the altitude of obstacles or interferences can be entered. 7. The device according to claim 6, characterized in that the microcomputer ( 14 ) has a memory with random access, in which the transit times or the associated height distances from the container for received sound / ultrasound echo signals can be stored. 8. Apparatus according to claim 6 or 7, characterized in that to the microcomputer ( 14 ) a distance display construction group ( 30 ) and a multiplying digital-to-analog converter ( 28 ) are connected, the output of which is connected to a control input ( 17 ) of the receiving amplifier ( 16 ) for setting the gain level connected and the second input ( 29 ) is connected to a temperature sensor in the container measuring temperature ( 38 ). 9. Device according to one of claims 6 to 8, characterized in that an input element is designed as a button ( 46 ), when actuated, the measured value of the transit time of the reflected sound / ultrasonic echo signal minus a small safety value by means of a programming cycle in the non-volatile memory ( 22 ) can be entered. 10. The device according to claim 9, characterized in that a further input element is designed as a button ( 44 ), when actuated, the measured values of the transit time of a sound / ultra sound echo generated by an obstacle or a defect or the distance of the obstacle or the defect from the tank bottom and the associated amplitudes of the sound / ultrasound echo waves can be entered into the non-volatile memory ( 22 ) by means of programming cycles. 11. The device according to claim 8, characterized in that the multiplying digital-to-analog converter ( 28 ) is followed by a switch ( 32 ) controllable by the microcomputer ( 14 ), to which an analog memory ( 34 ) is connected, which removes one arranged evaluation device is connected. 12. Device according to one of the An sayings 1 to 11, characterized, that the running times of the highest survey of the property over the Container bottom and the lowest point of the goods in the container for  any level can be measured and that the two Runtimes after averaging the fill level indicator can be used. 13. The apparatus according to claim 12, characterized in that an additional input element is designed as a button ( 48 ), the operation of the mean value formation is adjustable when actuated.