Radio probe for the secure transmission of measuring signals from an underground container system and its use on an underground tank

Abstract

Subsurface probe (1) for the secure transmission of measurement signals from an underground tank system (2), the subsurface probe (1) having at least one sensor (3) for recording measurement data, a transmission module (4) for transmitting digital signals to an above-ground gateway (7), a microcontroller (5) for controlling the at least one sensor (3) and the transmission module (4), and an autonomous power supply (6), characterized in that the transmission module (4) is designed to convert a narrowband measurement data signal of the sensor (3) into a signal with a larger bandwidth by means of a point-to-point transmission (8) with frequency spreading and to transmit it to the above-ground gateway (7), the frequency spreading being effected by a chirp spread spectrum, CSS, modulation, and a communication between the transmission module (4) and the gateway (7) taking place independently of the network protocol.

Description

[0001] The invention relates to a radio probe for the secure transmission of measurement signals from an underground container system, wherein the radio probe has at least one sensor for recording measurement data, a transmission module for transmitting digital signals to an above-ground gateway, a microcontroller for controlling the at least one sensor and the modem, and an autonomous power supply.

[0002] The invention also relates to the use of the radio probe according to the invention on an underground tank.

[0003] Storage containers, also known as tanks, for liquids and gases are increasingly being installed underground. While this has long been common practice at petrol and diesel filling stations, liquefied petroleum gas (LPG) storage containers are now often also being installed above ground.

[0004] Liquefied gas storage tank systems are subject to monitoring under the German Industrial Safety Ordinance (Betriebssicherheitsverordnung). They must therefore be inspected by an approved inspection body before commissioning and at regular intervals. The provisions of the Industrial Safety Ordinance regarding explosion protection must also be observed.

[0005] The fill level of storage tanks is increasingly being monitored remotely using electronic tank sensors in order to, among other things, make refueling logistics more effective.

[0006] It should be noted that such tank probes operate in a potentially explosive atmosphere, a so-called Ex zone, and must be designed to be intrinsically safe in accordance with the European ATEX Directive 2014 / 34 / EU. An Ex zone designates an area in which an explosive atmosphere consisting of a mixture of air with flammable substances in the form of gas, vapor, or mist is present continuously or for a long time.

[0007] State-of-the-art underground systems are known in which the fill level data from an intrinsically safe tank probe is transmitted via an intrinsically safe cable from an underground hazardous area to a GSM transmission gateway in the immediate vicinity of the tank and then sent via mobile communications to a logistics control center. This solution can generally be used at all tank locations but involves increased installation effort. Especially on sealed surfaces, such as gas stations, gardens, or paving, retrofitting is very complex or sometimes impossible due to the civil engineering work required to lay the cables.

[0008] Radio probes are often used on above-ground tanks because they eliminate the need for complex cabling and associated underground construction measures. Radio probes are defined as probes that can transmit their recorded data wirelessly. This is particularly advantageous when retrofitting existing tank systems. A cable-free radio probe is also technically elegant for compliance with explosion protection regulations. Previously known radio probes use common transmission methods such as direct radio in the ISM (Industrial, Scientific, and Medical) band at 433 MHz and 868 MHz, as well as mobile networks such as LTE.

[0009] Reliable operation via radio data transmission from underground domes and shafts is problematic because the radio signal is subject to high RF attenuation. Due to the surrounding soil, metal-clad domes, steel shaft covers, and the presence of vehicles parked over the shafts, the above-ground methods are not suitable for physical reasons, or at best only in isolated cases and with very limited application.

[0010] US 2006 / 0243345A1 describes a probe for above-ground tanks. It uses a standard ISM short-range transmission with 2-FSK modulation. However, this radio probe is unsuitable for use in underground shafts.

[0011] EP 3 462 144 A1 discloses a radio probe with Wi-Fi transmission. Wi-Fi uses OFDM (Orthogonal Frequency-Division Multiplexing) modulation. This transmission method is relatively resistant to signal interference. However, it uses a high carrier frequency (2.5 GHz or 5.6 GHz band), which prevents overcoming the underground dome and earth attenuation.

[0012] Most radio probes described in the prior art focus on the sensor technology and its technical implementation in a probe device. It is well known that wireless signal transmission is used for long or short distances. For applications above the earth's surface and in buildings, various point-to-point technologies and devices (ISM, PMR) as well as network-based systems (GSM, UMTS, LTE, 5G, WiFi, NB-IoT, LoRa-WAN) are available. Above ground, these technologies work more or less well. However, if a radio probe, as described in the prior art, is placed in an underground shaft, the attenuation is so high that error-free data transmission over a distance of just a few meters out of the earth is not possible at all, and only with great unreliability or high transmission power. This means thatA radio tank probe must be able to overcome the attenuation of the steel-clad and covered underground shafts, as well as the kilometers-long distance to the nearest mobile communications gateway. Without a remote antenna, i.e., without cable installation, this is only conceivable with very good network coverage and reduced attenuation, e.g., through the use of a plastic dome, and thus only at selected locations. The disadvantage of high transmission power is that such radio probes require large energy storage units, which is problematic in hazardous areas and during long periods of autonomous operation.

[0013] Therefore, two issues must always be considered when deploying a wireless solution: First, how can strong shaft attenuation be overcome? Second, is it possible to use the attenuated residual power to reach an IoT or LTE gateway and the internet?

[0014] Currently, it is common practice to deploy underground probes in hazardous areas with data transmission via an intrinsically safe cable or an integrated radio data modem with a remote (wired) external antenna. Due to its special design, an intrinsically safe cable ensures that no unsafe condition occurs even in the event of a fault.

[0015] The probe is powered by the device itself or intrinsically safe from the outside.

[0016] Unless an absolutely RF-tight space is artificially created through deliberate shielding measures, it can be assumed that naturally occurring shielding conditions will significantly reduce conventional RF propagation, but usually not completely suppress it. This is also the case with earth domes on underground storage facilities. However, the shielding is so strong that the commonly used radio technologies cannot be successfully deployed, as they are not intended for such specific applications. Mobile networks from GSM to 5G, and the NB-IoT networks based on them, serve users above ground, both outside and inside buildings and means of transport. However, even in traffic tunnels, basements, or parking garages below ground level, active repeaters and leaky RF cables (slotted cables) are usually required.Of course, such an effort is not possible for a probe in the Earth's dome.

[0017] LoRa probes for the wireless transmission of operating data from underground shafts are known from other applications, such as water and wastewater. However, these are always used in conjunction with a LoRa-WAN gateway. LoRa-WAN stands for Long Range Wide Area Network and means or enables energy-efficient transmission of data over long distances. The LoRa-WAN gateway forms the interface between the energy-efficient LoRa radio transmission and the high-performance connection to the server, whereby the low-power wireless network protocol must be used. The disadvantages, however, are the very different ranges due to shaft depths and distance from the gateway, as well as field interference caused by buildings, people, etc., which lead to significant transmission errors and correspondingly limited use.

[0018] It is therefore the object of the present invention to provide a radio probe which is suitable for underground use, in particular in earth shafts and earth domes, and which ensures a reliable transmission of measuring signals, in particular from an underground container system.

[0019] The object of the present invention is achieved by a radio probe according to the independent device claim 1.

[0020] The radio probe according to the invention for the secure transmission of measurement signals from an underground container system has at least one sensor for recording measurement data, a transmission module for transmitting digital signals to an above-ground gateway, a microcontroller for controlling the at least one sensor and the transmission module and an autonomous power supply, wherein the transmission module is designed to convert a narrowband measurement data signal from the sensor into a signal with a larger bandwidth by means of a point-to-point transmission with frequency spread and to transmit it to the above-ground gateway, wherein the frequency spread is carried out by chirp spread spectrum modulation (CSS), wherein communication between the transmission module and the gateway is network protocol-independent.

[0021] Network protocol-independent communication means that the sensor data collected by the radio probe and converted into an electrical signal is transmitted to a gateway using a point-to-point transmission with frequency spread using chirp spread spectrum modulation (CSS). This transmission is not tied to any specific network protocol. The gateway then serves to securely translate the transmitted data to the internet for further processing and forwarding within the network in use.

[0022] In one embodiment of the radio probe according to the invention, the transmission module is a LoRa modem, but without the LoRa modem being bound to a LoRa network protocol for communication in a LoRaWAN network.

[0023] The ability to use a transmission module with chirp spread spectrum (CSS) modulation for point-to-point transmission eliminates all of the aforementioned disadvantages of previously known radio technologies used in underground radio tank probes. A LoRa modem integrates CSS modulation functionality. The present invention therefore uses the well-known modulation technology in a modified form in a novel way for which it was not originally intended or developed.

[0024] The known spread spectrum modulation methods are actually designed to bridge the greatest possible distance between two points with low power or to filter a very attenuated useful signal from the noise. There are several different spreading methods. One of these is chirp spread spectrum modulation (CSS). This form of spread spectrum transmission uses so-called chirp pulses, in which the frequency varies over the duration of the pulse. This is exemplified in Fig. 1. A narrowband measurement data signal from the sensor is converted into a signal with a wider bandwidth, i.e., a bandwidth larger than that of the original measurement data signal from the sensor. This method is robust and does not require high-precision synchronization between the transmitter and receiver.

[0025] The present invention uses the CSS method under unusual conditions, namely short transmission length but with very high attenuation.

[0026] In one embodiment of the radio probe according to the invention, the above-ground gateway is arranged at a distance of 300 m, preferably 100 m, from the underground container system. This has the advantage that several radio probes according to the invention located within a 300 m, preferably 100 m radius of the gateway can use it jointly, and that the gateway can also be installed as a display terminal in a nearby building. The preferred embodiment of the radio probe with an above-ground gateway arranged at a distance of 100 m offers an optimal compromise between secure and reliable transmission of the modified measurement data signal from an underground earth dome to the above-ground gateway and secure further processing / transmission of the data to the Internet for the majority of applications and environmental conditions. The above-ground gateway does not have to be a LoRaWAN gateway.

[0027] In a further embodiment of the radio probe according to the invention, the radio probe comprises a Hall sensor for obtaining electronic filling data from mechanical-magnetic immersion probes.

[0028] In another embodiment of the radio probe according to the invention, the radio probe has a sensor for measuring temperature, a sensor for measuring pressure, a sensor for measuring humidity, or a sensor for measuring acceleration. This allows all important data that must be obtained from an Ex zone to be determined.

[0029] In a particularly advantageous manner, the radio probe according to the invention is used for the reliable wireless transmission of measurement signals from an underground container system to an above-ground gateway, according to claim 6, wherein the radio probe has at least one sensor for recording measurement data, a transmission module for transmitting digital signals to the above-ground gateway, a microcontroller for controlling the at least one sensor and the transmission module, and a self-sufficient power supply, wherein the transmission module is designed to convert a narrowband measurement data signal from the sensor into a signal with a larger bandwidth by means of a point-to-point transmission with frequency spread and to transmit it to the above-ground gateway, wherein the frequency spread is carried out by a chirp spread spectrum (CSS) modulation, wherein communication between the transmission module and the gateway is network protocol-independent,wherein the underground container system is designed as a tank in which a mechanical-magnetic submersible probe is arranged.,

[0030] Previous solutions for the remote transmission of measurement data from underground domes or other storage facilities, especially underground tanks, are associated with significant limitations that prevent the uniform, widespread remote monitoring of liquefied gas storage tanks. Wireless solutions using Bluetooth, industrial radio, or measurement radio (ISM) cannot overcome the high attenuation or do not sufficiently overcome it for long-distance transmission. Mobile radio (GSM, GPRS, UMTS, LTE) can only be used above the earth's surface. The transmission power is limited, for example, in the ISM (Industrial, Scientific, and Medical Band) or in conventional industrial radio, and would require excessive energy.

[0031] Furthermore, all previous solutions rely on cables: antenna cables, power supply cables, and intrinsically safe data cables. However, both the approval-related effort (ATEX Directive 2014 / 34 / EU) and the required civil engineering work for laying the cables make the systems more expensive to purchase and operate. Furthermore, varying equipment depending on the operating conditions poses problems for standardized control center design and data processing due to proprietary manufacturer protocols. This also hinders the increasing digitalization and networking of processes.

[0032] The present invention fundamentally changes the current situation described above. The solution described, in particular the use of the radio probe on underground tanks, can be used uniformly in all currently known scenarios for the remote transmission of measurement data, especially remote fill level transmission, even above ground. All components operate according to uniform, globally standardized, and generally approved radio procedures.

[0033] The invention will be explained in more detail below using an exemplary embodiment. Fig. 1 chirp pulse for use in chirp spread spectrum modulation (state of the art); Fig. 2 Radio probe according to the invention for use in an underground container system, in particular in an underground tank.

[0034] Fig. 2 shows an embodiment of the remote data transmission by means of the radio probe 1 according to the invention, which is ideally suited for use in an underground container system 2.

[0035] A radio probe 1 mounted in the underground shaft 2 on the liquid gas tank or other container system uses a Hall sensor 3 and downstream electronic data evaluation to determine the current container content in percent, or another measured value using another sensor 3, which is shown on the display of the probe 1. In parallel, the fill level data or other measured data are transmitted via a radio transmission module 4 with frequency spread modulation. This type of modulation enables the penetration of the shielding of the steel casing of the dome shaft 2 and the surrounding soil as well as the steel cover of the shaft. Measurement tests have proven that, depending on the depth and nature of the shaft, the signal can be received error-free above the earth's surface at distances of 50-300 m. This is technically sufficient for use outside of the potentially explosive area, e.g.An LTE gateway (7) is installed, which receives the fill level data or other measurement data via a suitable receiving modem and transmits it to the internet and to a server using, for example, the integrated LTE modem. This server stores the data in a database for archiving and further processing. Software scripts ensure appropriate data preparation. Visualization and remote operation of the system is browser-based at logistics workstations (9). Fig. Figure 2 shows schematically the described information flow.

[0036] The core idea of ​​the invention is to provide a radio probe for use in underground domes that uses the spread-frequency spectrum method for point-to-point transmission to an above-ground gateway, which transmits the received measured values ​​via LTE / 5G to a web-based telemetry control center. The use of the radio probe with a transmission module, particularly in combination with a submersible probe and in the form of a LoRa modem, which implements point-to-point transmission with spread-frequency spectrum, is particularly suitable for the unusual and therefore unobvious application in an underground tank container to solve the task at hand.

[0037] In a preferred configuration, the gateway is installed at a maximum distance of 100 m from the tank dome. Distances up to 300 m are also reliably feasible.

[0038] According to the invention, the LoRa-WAN technology for the radio probe is reduced to a short-range point-to-point connection from a heavily RF-shielded environment. However, a LoRa-WAN architecture with WAN gateways is completely dispensed with. A secure transmission range of a few meters, safely to the earth's surface, outside of an Ex zone, is sufficient.

[0039] The transmission part of the radio probe 1 is supplemented by a Hall sensor 3 with corresponding hardware and software environment and an ATEX-compliant autonomous power supply 6 with energy management.

[0040] According to the invention, the device, consisting of a point-to-point short-range connection and an LTE / 5G gateway with a radio transmission module, e.g., a LoRa modem, can also be used for probes with various sensors, e.g., for temperature, pressure, humidity, and acceleration, in environments with critical RF propagation conditions. For applications in hazardous areas, the intrinsic safety of all components used must always be ensured. List of reference symbols 1 radio probe 2 Underground tank system, earth shaft 3 Sensor 4 Transmission module, e.g., LoRa modem 5 microcontrollers 6 Power supply 7 Above-ground gateway 8 Point-to-point transmission 9 Web-based telemetry control center QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2006 / 0243345A1

[0010] EP 3 462 144 A1

[0011]

Claims

[1] Radio probe (1) for the secure transmission of measurement signals from an underground container system (2), wherein the radio probe (1) has at least one sensor (3) for recording measurement data, a transmission module (4) for transmitting digital signals to an above-ground gateway (7), a microcontroller (5) for controlling the at least one sensor (3) and the transmission module (4) and an autonomous power supply (6), characterized by that the transmission module (4) is designed to convert a narrowband measurement data signal of the sensor (3) into a signal with a larger bandwidth by means of a point-to-point transmission (8) with frequency spread and to transmit it to the above-ground gateway (7), wherein the frequency spread is carried out by a chirp spread spectrum, CSS, modulation, wherein communication between the transmission module (4) and the gateway (7) is network protocol-independent. [2] Radio probe (1) according to claim 1, characterized bythat the transmission module (4) is a LoRa module. [3] Radio probe (1) according to claim 1, characterized by that the above-ground gateway (7) is arranged at a distance of 300 m, preferably 100 m, from the underground container system (2). [4] Radio probe (1) according to claim 1, characterized by that the radio probe (1) comprises a Hall sensor for obtaining electronic filling data from mechanical-magnetic immersion probes. [5] Radio probe (1) according to claim 1, characterized by that the radio probe has a sensor (3) for measuring temperature or a sensor (3) for measuring pressure or a sensor (3) for measuring humidity or a sensor (3) for measuring acceleration. [6] Use of a radio probe (1) for the secure transmission of measurement signals from an underground container system (2) to an above-ground gateway (7), wherein the radio probe (1) has at least one sensor (3) for recording measurement data, a modem (4) for transmitting digital signals to the above-ground gateway (7), a microcontroller (5) for controlling the at least one sensor (3) and the modem (4) and an autonomous power supply (6), wherein the modem (4) is designed to convert a narrowband measurement data signal of the sensor (3) into a signal with a larger bandwidth by means of a point-to-point transmission (8) with frequency spread and to transmit it to the above-ground gateway (7), wherein the frequency spread is carried out by a chirp spread spectrum, CSS, modulation, wherein the underground container system (2) is designed as a tank in which a mechanical-magnetic submersible probe is arranged.

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