Radar level gauge system with feeding comprising an electrical filter

A radar level gauge system, for determining a filling level of a product in a tank, said radar level gauge system comprising:

• a transmission line probe arranged inside said tank for guiding an electromagnetic transmit signal towards a surface of said product, and for returning an electromagnetic surface echo signal resulting from reflection of said transmit signal at said surface;
• a tank feed-through for mechanically attaching said transmission line probe to a tank wall of said tank through a non-conductive mechanical connection between said transmission line probe and said tank wall, and for providing a conductive electrical connection to said transmission line probe from outside said tank;
• a measurement electronics unit arranged outside said tank including:
• a transceiver arranged outside said tank for generating said transmit signal, transmitting said transmit signal, and receiving said surface echo signal;
• an electrical filter circuit arranged outside said tank, said electric filter circuit having an input coupled to said transceiver and an output coupled to said transmission line probe via said tank feed-through for providing said transmit signal from said transceiver to said transmission line probe and said surface echo signal from said transmission line probe to said transceiver, said electrical filter circuit exhibiting a series capacitance for non-conductively coupling said transceiver to said transmission line probe via said tank feed-through;
• and
• processing circuitry arranged outside said tank and connected to said transceiver for determining said filling level based on a timing relation between said transmit signal and said surface echo signal, wherein:
• a maximum possible voltage that may be present in said measurement electronics unit is at least 100 V and less than 375 V, and exhibits an AC frequency in a first frequency band only including frequencies lower than 100 Hz;
• and
• said electrical filter circuit is dimensioned in such a way that an amount of energy in said first frequency band that can be stored by the series capacitance of said electrical filter at said maximum possible voltage is insufficient to ignite a hydrogen/air mixture with 22% hydrogen gas.