Apparatus for interface measurement in a storage tank

A method for measuring the water level at the bottom of a storage tank, the water level being the product-water interface between product and water within the storage tank, the method comprising the following steps:

• (a) exciting a plurality of open-circuited quarter wave co-axial transmission lines with signals in each transmission line, each transmission line having at its open end a probe surrounded with an insulated material, each probe having been positioned within the storage tank with a different height with respect to the bottom of the tank such that at least one of the probes has a portion of that probe in contact with the product-water interface;
• (b) reflecting the signals from the probes;
• and
• (c) determining from different voltage amplitudes of the reflected signals the product-water interface level in the storage tank by comparing each reflected signal's amplitude with a look up table, the look up table providing the product-water interface level corresponding to the amplitudes of the reflected signals.

An apparatus for measuring the water level at the bottom of a storage tank, the water level being the product-water interface between product and water within the storage tank, the apparatus comprising:

• a sensor assembly adapted to be located at the tank bottom, said assembly having a plurality of measurement sensors arranged in a housing provided with slots for product and water to enter and leave the housing;
• each measurement sensor comprising an open-circuited co-axial transmission line having at its open end a probe, the probe being surrounded with an insulated material and functioning as a monopole antenna, each sensor being arranged at a different height within the housing to cover a measurement range;
• a means for exciting each transmission line with signals;
• and
• a means for determining the water level from amplitudes of signals reflected from each probe by comparing each reflected signal's amplitude with a look up table, the look up table providing the water level corresponding to the amplitudes of the reflected signals.

A method for measuring the water level at the bottom of a storage tank, the water level being the product-water interface between product and water within the storage tank, the method comprising the following steps:

• (a) exciting a plurality of open-circuited co-axial transmission lines with signals in each transmission line, each transmission line having at each of its open ends a probe surrounded with an insulated material, each probe having been positioned within the storage tank with a different height with respect to the bottom of the tank such that at least one of the probes has a portion of that probe in contact with the product-water interface;
• (b) reflecting the signals from the probes;
• and
• (c) determining from different voltage amplitudes of the reflected signals the product-water interface level in the storage tank by comparing each reflected signal's amplitude with a look up table, the look up table providing the product-water interface level corresponding to the amplitudes of the reflected signals.