DE102018113232A1 - Radar-based level gauge - Google Patents

Abstract

The invention relates to a filling level measuring device (1) for measuring the filling level (L) of a filling material (3) located in a container (2), and to a corresponding method for operating this level measuring device (1). According to the invention, the level gauge (1) has an acceleration sensor and / or a rotation rate sensor for measuring an acceleration and / or a rotation rate in order to detect any movements of the container (1). In this case, the level gauge (1) changes the clock rate (r) if an acceleration and / or a rotation rate is measured. This design makes it possible to operate the level gauge (1) performance optimized and therefore self-sufficient to non-stationary containers (1), such as IBC tanks: Since the power consumption of the level measuring device (1) significantly depends on the clock rate (r), can a reduced clock rate (r) the level gauge (1) depending on the situation are operated in an energy-saving mode.

Description

The invention relates to a stand-alone fill level measuring device and a method for its operation.

In process automation technology, appropriate field devices are used to record relevant process parameters. For the purpose of detecting the process parameters, suitable measuring principles are therefore implemented in the respective field devices with which the corresponding process parameters such as level, flow, pressure, temperature, pH, redox potential or conductivity can be detected. Various types of field device types are manufactured and distributed by Endress + Hauser.

Non-contact measuring methods have become established for level measurement of products in containers since they are robust and require little maintenance. Another advantage of non-contact measuring methods is the ability to measure the level virtually continuously. In the field of continuous level measurement, radar-based measuring methods are therefore predominantly used (in the context of this patent application, the term "radar" is defined as a signal or electromagnetic wave with frequencies between 0.03 GHz and 300 GHz). The two common measuring principles are the pulse-transit time principle (also known by the term "pulse radar") and the FMCW principle ("Frequency Modulated Continuous Wave", in English: "Frequency-modulated continuous wave radar").

At radar frequencies of about 20 GHz and higher, the transmission circuit of the level gauge can be realized together with the receiving circuit and subsequent evaluation as a common integrated circuit. In addition, the dimension of the antennas to be used decreases with increasing frequency. Therefore, level gauges can be realized at higher radar frequencies in principle space-saving and better mountable.

If the level gauge is compact, especially with regard to the overall height, and the level to be measured can be measured with sufficient resolution, level gauges can in principle also be used on non-stationary containers such as IBC tanks. However, the use of such containers fail because the level gauge can only be operated wired due to its power consumption.

The invention is therefore based on the object to provide a stand-alone operable level gauge.

• - Ein Sende-/Empfangsmodul, das ausgelegt ist,
  • ◯ ein hochfrequentes Signal mit einer vordefinierten Taktrate in Richtung des Füllgutes auszusenden, und
  • ◯ nach Reflektion an der Oberfläche des Füllgutes ein entsprechendes Empfangssignal zu empfangen,
• - Eine Auswerte-Schaltung, die ausgelegt ist, zumindest anhand des Empfangssignals den Füllstand entsprechend der Taktrate jeweils erneut zu bestimmen.

The invention solves this problem by a level gauge for measuring the level of a filling material located in a container. For this the measuring device comprises the following components:

• - A transceiver module that is designed
  • ◯ send a high-frequency signal at a predefined cycle rate in the direction of the contents, and
  • ◯ to receive a corresponding received signal after reflection at the surface of the filling material,
• An evaluation circuit which is designed to determine the fill level corresponding to the clock rate in each case at least based on the received signal.

Depending on the measuring principle (FMCW or pulse transit time method), the transmitting / receiving module and the evaluation circuit can be realized on the basis of known circuit components: In the case of FMCW, the transmitting block can be based on a PLL ("Phase Locked Loop"). be built up; The evaluation circuit can determine the distance or fill level by FFT ("Fast Fourier Transformation") of the received signal by means of a corresponding computing block.

In implementation of the pulse transit time method, the corresponding radar pulses in the transmission block of the transmission / reception module are generally generated by a cyclically controlled oscillator, for example a voltage-controlled oscillator or merely a quartz oscillator. The receive block processes the received signal in the pulse transit time method by sampling. Based on the sampled signal, the evaluation circuit determines the distance or the level. The functional principle of FMCW and pulse radar-based level gauges is described, for example, in "Radar Level Measurement"; Peter Devine, 2000.

• - Einen Beschleunigungssensor und/oder einen Drehratensensor zur Messung einer Beschleunigung und/oder einer Drehrate.

According to the invention, the fill level measuring device also comprises, in addition to these components known from the prior art:

• - An acceleration sensor and / or a rotation rate sensor for measuring an acceleration and / or a rotation rate.

In this case, the evaluation circuit is designed so that the clock rate is changed, provided that an acceleration and / or a rotation rate is measured by the acceleration sensor or the rotation rate sensor.

In the context of the invention, the term "clock rate" is the rate at which in each case a new measurement of the fill level per time he follows. Depending on the measuring method implemented, the clock rate thus results in different ways: In the case of the pulse transit time method, the clock rate corresponds to a corresponding minimum number of cyclically received pulses or measuring signals which must be used to determine a fill level measured value after scanning the received signals. In the FMCW method, the per se continuous radar signal is interrupted in cycles with a predefined interruption duration or transmitted with a predefined transmission duration. Thus, the clock rate at FMCW corresponds to the reciprocal of the sum of transmit duration and break duration.

• - Aussenden des Radar-Signals in Richtung des Füllgutes mit einer vordefinierten Taktrate,
• - Empfang des Empfangssignals nach Reflektion des Radar-Signals an der Oberfläche des Füllgutes,
• - Taktweise Neubestimmung des Füllstandes entsprechend der Taktrate anhand zumindest des Empfangssignals, und
• - Änderung der Taktrate, sofern eine Beschleunigung und/oder eine Drehrate am Füllstandsmessgerät gemessen wird.

Analogously to the level measuring device according to the invention, the invention is also achieved by a corresponding method for its operation. After that, the method comprises the following method steps:

• Emitting the radar signal in the direction of the contents at a predefined clock rate,
• Receiving the received signal after reflection of the radar signal at the surface of the filling material,
• - Timed redetermination of the level according to the clock rate based on at least the received signal, and
• - Change in the clock rate, if an acceleration and / or a rotation rate is measured on the level gauge.

By this design according to the invention, it is possible to operate the level gauge performance optimized and therefore self-sufficient. Since the power consumption of the level gauge depends largely on the clock rate, the level gauge can be operated in an energy-saving mode by a reduced clock rate. Only if necessary, the clock rate is increased. In this case, the setting of the clock rate is made dependent on whether the container is currently resting stationary, or undergoes an acceleration / rotation rate, for example by a possible transport or a loading or unloading. In the simplest embodiment, the clock rate can only be switched between "high" and "low" clock rates such as ten measurements per second and one measurement per hour. Accordingly, only a sufficiently sized battery or accumulator for powering the level gauge needs to be used. On a wired power supply can be omitted.

By being able to decide for yourself whether it can be measured in an energy-saving mode, the level gauge according to the invention can also be used on potentially non-stationary containers such as IBC tanks. Accordingly, when used on an IBC tank, a suitable fastener for attachment to an IBC tank should be provided. In this case, it is particularly appropriate to use the screw hole on the top of the IBC tank for attachment. If the transmitter / receiver module on the hardware side is designed so that it transmits the radar signal with a frequency of at least 20 GHz, the level gauge can also be made correspondingly compact.

The appropriate strategy of the clock rate change is inventively dependent on the particular use scenario: On the one hand, the clock rate, starting from a very low clock rate, for example, a maximum of one measurement per hour or even only one measurement per day, increased if one Acceleration, a rate of rotation or both is measured. This makes sense, for example, if it is known according to the use scenario that the container is moved or tilted only for the purpose of filling / emptying and no level change is to be expected at standstill. If necessary, it also makes sense in such a case to increase the clock rate only when, in addition to the acceleration and / or the rotation rate, a certain minimum change in the fill level is also detected. In this case, the threshold of the minimum change is to be dimensioned such that fluctuations due to vibrations or waves remain unconsidered.

Even with other application scenarios, it may be advantageous to change the clock rate only, if in addition to the acceleration / rotation rate and a change in the level is detected. In further application scenarios, it may in turn make sense to reduce the clock rate or, in extreme cases, to completely stop the level measurements, provided that an acceleration and / or a rotation rate is measured. This can be advantageous, for example, if it is known from the field of application of the container that during transport or during filling / emptying such a high acceleration or vibration acts that during this time from the outset no meaningful level measurement will be possible.

Not only in this context, it is conceivable that the clock rate is changed only with a defined time delay after an acceleration and / or a rate of rotation is measured: So it may come after the end of the acceleration in a known decay time to Nachschwappen the contents, so that an adjustment of the clock rate only makes sense after this cooldown.

• 1: eine schematische Anordnung des erfindungsgemäßen Füllstandsmessgerät an einem Behälter.

With reference to the following figure, the invention will be explained in more detail. It shows:

• 1 : A schematic arrangement of the level measuring device according to the invention on a container.

To understand the invention shows 1 an inventive level measuring device 1 attached to the top screw opening of an IBC tank 2 is attached. Inside the IBC tank 2 there is a filling material 3 whose level L through the level gauge 1 is to be determined. Here is the installation height H of the level gauge 1 relative to the tank bottom due to the dimensions of the IBC tank 2 known.

The level gauge 1 is like that at the IBC tank 2 aligned that it radar signals S _HF with a predefined clock rate _c in the direction of the surface of the filling 3 sending out. Here, the cycle time is divided, the clock rate _c corresponds to a transmission duration plus a pause duration or a corresponding transmission-to-pause ratio. After reflection of the radar signals S _HF The filling level measuring device receives at the product surface 1 corresponding reception signal E _HF as a function of the distance d = h-L to the product surface after a corresponding transit time.

Level gauges based on the pulsed radar principle are the radar signals S _HF Radar pulses transmitted cyclically, so that on the basis of the pulse transit time between emission of a pulse-shaped transmission signal S _HF and receiving the corresponding pulse-shaped received signal R _HF immediately the distance d and thus the level L can be determined. In the case of FMCW radar, it is the single radar signal S _HF around a continuous radar signal. However, the radar signal points S _HF in this case, within a predefined frequency band, a sawtooth frequency change. Accordingly, the duration and thus the distance or the level L when implementing the FMCW method based on the instantaneous frequency difference between the currently received received signal E _HF and the radar signal transmitted at the same time S _HF be determined.

bzw. eine Drehrate $\overrightarrow{d}$

zu detektieren. Dies kann je nach Einsatz-Szenario des IBC-Tanks verschiedenen Ursachen zugeordnet werden:

• ob der IBC-Tank momentan stationär ruht, oder ob er beispielsweise zwecks Befüllung bzw. Entleerung geneigt wird. Sofern eine hierdurch bedingte Beschleunigung $\overrightarrow{a}$
  
  /Drehrate $\overrightarrow{d}$
  
  gemessen wird, kann das Füllstandsmessgerät 1 erfindungsgemäß seine Taktrate r_c entsprechend ändern.

This in 1 illustrated level gauge 1 according to the invention additionally comprises an acceleration sensor or a rotation rate sensor. Thus it is possible to accelerate $\overrightarrow{a}$

or a rotation rate $\overrightarrow{d}$

to detect. Depending on the application scenario of the IBC tank, this can be assigned to different causes:

• whether the IBC tank is currently stationary, or whether it is inclined, for example, for filling or emptying. If a resulting acceleration $\overrightarrow{a}$
  
  / Rate $\overrightarrow{d}$
  
  is measured, the level gauge can 1 According to the invention change its clock rate r _c accordingly.

/Drehrate $\overrightarrow{d}$

zu erhöhen, wenn sich der neue Füllstand nach Beenden der Befüllung/Entleerung eingependelt hat.Thus, the level gauge measures 1 only with a high clock rate, if this really makes sense or if an intensive monitoring of the level L is required. In this case, a high clock rate, for example, fail with a maximum of 10 measurements per minute or at most 10 measurements per second. For example, measuring at a high clock rate r _c might make sense to quickly change the level during filling / draining L to be able to measure. Depending on the application scenario, a filling / emptying by means of the acceleration sensor or yaw rate sensor can be detected if this is accompanied, for example, by vibrations or tilting of the IBC tank. In a slightly modified operating mode, it is also conceivable to set the clock rate for a short period of time after completion of the acceleration $\overrightarrow{a}$

/ Rate $\overrightarrow{d}$

increase when the new level has settled after completion of the filling / emptying.

oder einer Drehrate $\overrightarrow{d}$

wiederum in einem momentanen Transport des IBC-Tanks 2 liegen. Einerseits kann es in diesem Fall erwünscht sein, das Füllstandsmessgerät 1 während des Transportes möglichst leistungssparend zu betreiben und dementsprechend die Taktrate r_c zu reduzieren, da bekanntermaßen während dieser Zeit keine Befüllung bzw. Entleerung stattfinden kann. Bei Reduktion der Taktrate r_c auf null kann entsprechend der letzte, vor Auftreten der Beschleunigung $\overrightarrow{a}$

gemessene Füllstandswert L als aktueller Füllstandswert L im Füllstandsmessgerät 1 bzw. einer übergeordneten Einheit 4 hinterlegt werden.In other application scenarios, the cause of an acceleration $\overrightarrow{a}$

or a rotation rate $\overrightarrow{d}$

again in a current transport of the IBC tank 2 lie. On the one hand, it may be desirable in this case, the level gauge 1 to operate as efficiently as possible during transport and accordingly to reduce the clock rate r _c , since, as is known, no filling or emptying can take place during this time. When the clock rate r _{c is} reduced to zero, the last one can occur before the acceleration occurs $\overrightarrow{a}$

measured level value L as current level value L in the level gauge 1 or a higher-level unit 4 be deposited.

oder Drehrate $\overrightarrow{d}$

mehr gemessen wird, stellt das Füllstandsmessgerät 1 wieder auf eine geringe Taktrate r_c um und wechselt somit in einen energiesparenden Modus.It would be advantageous depending on the type of container 2 but also to increase the clock rate r _c, in particular during transport to the level L due to potential leakage or spillover during this period. After the end of the transport, or after no acceleration $\overrightarrow{a}$

or rate of rotation $\overrightarrow{d}$

is measured more, represents the level gauge 1 back to a low clock rate r _c and thus switches to an energy-saving mode.

In the illustrated embodiment, the level gauge is 1 via an interface, such as "PROFIBUS", "HART", "Wireless HART" or "Ethernet" with a higher-level unit 4 , such as A remote accessable database or local process control system. This can be the level value L be transmitted. But it can also other information, such as the current position or position of the level gauge 1 or the container 2 be communicated. In this context, it would also be conceivable that the preset clock rate (s) r _{c can} be manually reconfigured via this interface. This is justified, for example, if the level gauge 1 another container 2 assigned to a different deployment scenario than that of the previous container 2 subject.

LIST OF REFERENCE NUMBERS

1

level meter

2

container

3

filling

4

Parent unit

d

distance

R _HF

receive signal

acceleration

rotation rate

H

installation height

L

level

_c

clock speed

S _HF

Radar Signal

Claims (10)

Level measuring device for measuring the filling level (L) of a filling material (3) located in a container (2), comprising: - a transmitting / receiving module which is designed, ◯ a radar signal (S _HF ) having a predefined clock rate (r _c ) in the direction of the filling material (3), and ◯ after reflection on the surface of the filling material (3) to receive a corresponding received signal (R _HF ), - an evaluation circuit which is designed, at least based on the received signal (R _HF ) to determine the level (L) according to the clock rate (r _c ), characterized by - an acceleration sensor and / or a rotation rate sensor for measuring an acceleration $\left(\overrightarrow{a}\right)$

and / or a rate of rotation $\left(\overrightarrow{d}\right)$

wherein the evaluation circuit is adapted to change the clock rate (r _c ), provided an acceleration $\left(\overrightarrow{a}\right)$

and / or a rotation rate $\left(\overrightarrow{d}\right)$

is measured. Level gauge after Claim 1 , wherein a battery or an accumulator for supplying energy to the level measuring device is provided. Level gauge after Claim 1 or 2 , wherein a fastening means for attachment to an IBC tank (2), in particular at a screw opening of the IBC tank (2), is provided. Level gauge according to one of the preceding claims, wherein the transceiver module is adapted to emit the radar signal (S _HF ) at a frequency of at least 20 GHz. Method for operating the level measuring device according to one of the preceding claims, comprising the following method steps: emitting the radar signal (S _HF ) in the direction of the filling material (3) at a predefined clock rate (r _c ), receiving the received signal (R _HF ) Reflection of the high-frequency signal (S _HF ) on the surface of the filling material (3), - Timing redetermination of the level (L) according to the clock rate (r _c ) based on at least the received signal (R _HF ), and - Changing the clock rate (r _c ) if an acceleration $\left(\overrightarrow{a}\right)$

and / or a rotation rate $\left(\overrightarrow{d}\right)$

at the level gauge (1) is measured. Method according to Claim 5 , wherein the clock rate (r _c ) is increased, provided an acceleration $\left(\overrightarrow{a}\right)$

and / or a rotation rate $\left(\overrightarrow{d}\right)$

is measured. Method according to Claim 5 , wherein the clock rate (r _c ) is reduced, provided an acceleration $\left(\overrightarrow{a}\right)$

and / or a rotation rate $\left(\overrightarrow{d}\right)$

is measured. Method according to one of claims 5 to 7, wherein the clock rate (r _c ) is changed, if a change of the level (L) is detected. Method according to one of claims 5 to 8, wherein a clock rate (r _c ) of a maximum of two measurements per hour is set. Method according to one of claims 5 to 9, wherein the clock rate (r _c ) is changed with a defined time delay after an acceleration $\left(\overrightarrow{a}\right)$

and / or a rotation rate $\left(\overrightarrow{d}\right)$

is measured.

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