# US 10,480,985 B2 · Explosion proof radar level gauge > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,480,985 B2 - Document ID: US10480985B2 - Status: Granted - Kind: B2 - Application number: 15/720,031 - Filed: 2017-09-29 - Published: 2019-04-04 - Granted: 2019-11-19 - Earliest claimed: 2017-09-29 - Assignees: Rosemount Tank Radar AB - Applicants: Rosemount Tank Radar AB - Inventors: Mikael Kleman; Leif Nilsson - Web page: https://patentgrep.com/patent/US10480985B2 ## CPC - G01F 23/284: Electromagnetic waves - G01S 13/88: Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00) - H01Q 1/225: {used in level-measurement devices, e.g. for level gauge measurement} - G01S 7/003: {Transmission of data between radar, sonar or lidar systems and remote stations} - G01S 7/027: {Constructional details of housings, e.g. form, type, material or ruggedness} - G01S 7/032: {Constructional details for solid-state radar subsystems} - G01S 13/08: Systems for measuring distance only (indirect measurement G01S13/46) - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract A radar level gauge comprising a housing enclosing a compartment providing explosion proof protection, RLG circuitry located inside compartment, which circuitry is incompatible with intrinsic safety requirements, and a signal propagation device located outside the compartment. The housing has an explosion proof first signal passage providing a transmission line for the microwave transmit signal, and an explosion proof second signal passage in providing a two-wire interface for electrically conductively connecting the radar level gauge to an intrinsically safe system located externally of the radar level gauge. Further, the RLG includes an electrical barrier connected between the RLG circuitry and the two-wire interface, the electrical barrier preventing energy and/or thermal energy in the RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface. ## Claims ### Claim 1 A radar level gauge for determining the filling level of product in a tank, said gauge comprising: a housing with a housing wall enclosing a compartment providing explosion proof protection; RLG circuitry located inside compartment, said circuitry in use having an available electrical and/or thermal energy incompatible with intrinsic safety requirements; a signal propagation device located outside said compartment, said signal propagation device being adapted to direct a microwave transmit signal toward said product and return reflections thereof from a surface of said product; an explosion proof first signal passage in said housing wall, said first signal passage providing a transmission line for said microwave transmit signal between said RLG circuitry and said signal propagation device; an explosion proof second signal passage in said housing wall, said second signal passage providing a two-wire interface for electrically conductively connecting said radar level gauge to an intrinsically safe system located externally of said radar level gauge, to provide at least one of: communication between said radar level gauge and said intrinsically safe system, and power supply to said RLG circuitry; and an electrical barrier connected between said RLG circuitry and the two-wire interface, said electrical barrier preventing energy or voltages in said RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface. ### Claim 2 (depends on 1) The radar level gauge according to claim 1, wherein said RLG circuitry includes at least one energy store having an energy storage capacity which is incompatible with IS requirements at a voltage applied to the storage capacity. ### Claim 3 (depends on 1) The radar level gauge according to claim 1, wherein said RLG circuitry includes at least one energy store having an energy storage capacity greater than 600 μJ. ### Claim 4 (depends on 1) The radar level gauge according to claim 1, wherein said RLG circuitry includes one of: a capacitance of at least 100 μF with a voltage across the capacitance of at least 5 V, a capacitance of at least 25 μF with a voltage across the capacitance of at least 6.5 V, a capacitance of at least 10 μF with a voltage across the capacitance of at least 8 V, a capacitance of at least 2 μF with a voltage across the capacitance of at least 12 V, and a capacitance of at least 0.5 μF with a voltage across the capacitance of at least 16 V. ### Claim 5 (depends on 1) The radar level gauge according to claim 1, wherein the electrical barrier includes at least one first diode connected in series between the RLG circuitry and the two-wire interface, thereby preventing energy from said RLG circuitry from reaching an intrinsically safe system connected the two-wire interface. ### Claim 6 (depends on 5) The radar level gauge according to claim 5, wherein the electrical barrier includes at least one fuse and/or one resistor limiting a current and/or a power said at least one first diode is subjected to. ### Claim 7 (depends on 1) The radar level gauge according to claim 1, wherein the electrical barrier includes at least one second diode connected in parallel between lines of the two-wire interface, thereby preventing negative voltages at the two-wire interface. ### Claim 8 (depends on 7) The radar level gauge according to claim 7, wherein the electrical barrier includes at least one fuse and/or one resistor limiting a current and/or a power said at least one second diode is subjected to. ### Claim 9 (depends on 1) The radar level gauge according to claim 1, wherein said first explosion proof passage is adapted to ensure that high frequency energy transmitted through the first passage comply with requirements defined in clause 6.6.1 of IEC 60079-0. ### Claim 10 (depends on 1) The radar level gauge according to claim 1, wherein said compartment and said first and second passages comply with the Ex-d requirements of IEC 60079-1. ### Claim 11 (depends on 1) The radar level gauge according to claim 1, wherein said intrinsically safe system complies with the Ex-ia requirements of IEC 60079-11. ### Claim 12 (depends on 1) The radar level gauge according to claim 1, wherein said signal propagation device is a directional antenna. ### Claim 13 (depends on 12) The radar level gauge according to claim 12, wherein said first signal passage includes a waveguide with a dielectric filling member made of a structurally strong and temperature resistant material. ### Claim 14 (depends on 1) The radar level gauge according to claim 1, wherein said signal propagation device is a transmission line probe. ### Claim 15 (depends on 14) The radar level gauge according to claim 14, wherein said first signal passage includes an electrical filter circuit having an input coupled to the RLG circuitry and an output coupled to the transmission line probe, the electrical filter circuit exhibiting a series capacitance for non-conductively coupling the RLG circuitry to the transmission line probe. ### Claim 16 (depends on 1) The radar level gauge according to claim 1, wherein the transmit signal has a frequency greater than 1 GHz. ### Claim 17 (depends on 1) The radar level gauge according to claim 1, wherein said RLG circuitry includes: transceiver circuitry configured to generate and transmit an electromagnetic transmit signal ST and receive an electromagnetic return signal reflected from the tank, processing circuitry configured to determine the distance between a reference position and the surface of the product based on a relationship between the transmit signal and the return signal, and signal/power circuitry configured to receive operating power and communicate measurement data.