Close proximity material interface detection for a microwave level transmitter

A method of detecting a twin peak pulse in a waveform and time locations of first and second overlapping received wave pulses of the twin peak pulse, the waveform is generated by a pulse receiver of a microwave level transmitter used to detect material levels in a tank, the first and second received wave pulses corresponding to first and second material interfaces, respectively, the method comprising:

• (a) detecting a starting point of the waveform having an amplitude that at least meets a first threshold value corresponding to the first received wave pulse;
• (b) detecting a first peak point along the waveform, after detecting the starting point, where a slope sign of the waveform changes and, after which, the amplitude of the waveform changes by an amount that exceeds a noise margin prior to the slope sign of the waveform changing, wherein the first peak point relates to the time location of the first material interface;
• (c) detecting a valley along the waveform, after detecting the first peak point, where the slope sign of the waveform changes and, after which, the amplitude of the waveform changes by an amount that exceeds the noise margin prior to the slope sign of the waveform changing, wherein the existence of the first peak point and the valley indicates that the waveform contains a twin peak pulse;
• and
• (d) detecting a second peak point along the waveform, after the valley, relating to the time location of the second material interface, whereby the levels of the first and second material interfaces can be calculated using the first and second peak points, respectively.

A microwave level transmitter used to determine levels of first and second materials contained in a tank, the levels of first and second materials corresponding to first and second material interfaces, respectively, the microwave level transmitter comprising:

• a pulse generator adapted to transmit a microwave pulse into the first and second materials using a radar antenna;
• a pulse receiver electronically coupled to the radar antenna and adapted to produce a waveform;
• an interface detecting module for detecting a twin peak pulse in the waveform having first and second overlapping received wave pulses corresponding to the first and second material interfaces, respectively, the interface detecting module adapted to:
• detect a first peak point of the waveform corresponding to the first received wave pulse;
• and
• detect a valley of the waveform after detecting the first peak point, wherein the detection of the first peak point and the valley indicates that the waveform contains a twin peak pulse;
• detect a second peak point relating to the second material interface when the waveform contains a twin peak pulse;
• and
• produce interface detection information relating to the first and second peak points when the waveform contains a twin peak pulse;
• and
• a level calculating module coupled to the interface locating module and adapted to calculate the levels of the first and second material interfaces using the interface detection information.

A computer readable medium having stored thereon instructions, executable by an embedded controller in a microwave level transmitter used to detect material levels in a tank, to cause the transmitter to detect a twin peak pulse in a waveform, the twin peak pulse including overlapping first and second received wave pulses reflected from first and second material interfaces, respectively, the instructions comprising:

• (a) detecting a first peak point of the waveform corresponding to the first received wave pulse;
• whereby a level of the first material interface can be calculated using the first peak point;
• and
• (b) detecting a valley of the waveform after detecting the first peak point, wherein the detection of the first peak point and the valley indicates that the waveform contains a twin peak pulse.