Patent ID: 7098669

Claim:
A system for determining the depth of a fluid in a storage tank, wherein the depth of the fluid is determined after the detection of a pulsed wave that is reflected from the top surface of the fluid, the system comprising: a. a transducer configured to measure the reflected pulsed wave and to generate an analog input signal that corresponds to the reflected pulsed wave; b. an analog-to-digital converter that is coupled to the transducer, and configured to convert the analog input signal into a digital input signal; and c. a filter that is coupled to the analog-to-digital converter, wherein the filter includes a finite impulse response filter that is configured to receive the digital input signal and to generate a digital output signal, the finite impulse response filter including: i. a two-stage shift register, ii. a first subtractor that is coupled to the two-stage shift register, iii. an n/2-stage shift register that is coupled to the first subtractor, where n is an even integer greater than or equal to four, iv. a second subtractor that is coupled to both the first subtractor and the n/2-stage shift register, v. an adder that is coupled to the second subtractor, and vi. a storage register that is coupled to the adder.