Electronic multi-purpose material level sensor

A method for sensing the surface or interface level of a material comprising the steps of:

• electrically coupling a conductor to a guide wire;
• connecting a launcher plate between said conductor and guide wire;
• immersing said guide wire at least partially in the material;
• inputting electrical transmit pulses into said conductor, said transmit pulses being conducted over said conductor to said launcher plate, said launcher plate acting as a transmit antenna ground plane, and helping launch said electrical pulses into said guide wire as near field, guided electromagnetic (EM) waves, and also producing a fiducial pulse back into the conductor;
• waiting for a period of time (T.sub.SAMP);
• said EM waves propagating along said guide wire, and being at least partially reflected by the surface or interface;
• said reflected EM waves propagating back along said guide wire toward said launcher plate, said launcher plate acting as a receive antenna ground plane, and therefrom said reflected EM waves being transmitted as reflected pulses to said conductor;
• opening a gate to allow said reflected pulses to be sampled;
• repeating said waiting and opening steps at about 10 kHz to 10 MHz rate, for allowing approximately 10 to 10,000 reflected pulses to be averaged prior to incrementing T.sub.SAMP ;
• and
• determining a time delay between said fiducial and reflected pulses, thus establishing the surface or interface level relative to said launcher plate.

A sensor for determining the surface or interface level of a material comprising:

• a pulse generator for generating electrical transmit pulses;
• a guide wire at least partially immersed in the material;
• a conductor electrically coupling said pulse generator and said guide wire, for conducting said transmit pulses to said guide wire as near field, guided electromagnetic (EM) waves, such that said EM waves are at least partially reflected by the surface or interface and converted to corresponding electrical reflected pulses;
• a sampler connected to the conductor for sampling said reflected pulses and consisting of a single diode;
• and
• circuitry connected to the pulse generator and sampler for determining a time delay between said transmitted and reflected pulses for establishing the surface or interface level.

A sensor for determining the surface or interface level of a material comprising:

• a pulse generator for generating electrical transmit pulses;
• a guide wire at least partially immersed in the material;
• a conductor electrically coupling said pulse generator and said guide wire, for conducting said transmit pulses to said guide wire as near field, guided electromagnetic (EM) waves, such that said EM waves are at least partially reflected by the surface or interface and converted to corresponding electrical reflected pulses;
• a sample and hold circuit connected to the conductor for receiving said reflected pulses;
• an exponential range delay circuit connected between the pulse generator and sample and hold circuit for controlling the timing of gate pulses transmitted to the sample and hold circuit;
• and
• circuitry connected to the pulse generator and sample and hold circuit for determining a time delay between said transmitted and reflected pulses for establishing the surface or interface level.

In a sensor for determining the surface or interface level of a material, apparatus comprising:

• a pulse repetition interval generator;
• a transmit pulse generator connected to the pulse repetition interval generator;
• a differentiation capacitor connected to the transmit pulse generator;
• a termination resistor connected from the differentiation capacitor to ground;
• a conductor having a first end connected to the differentiation capacitor and termination resistor;
• a transmission line connected to a second end of the conductor and being immersible into the material;
• a high input impedance sampler having a first input connected to the first end of the conductor;
• a hold capacitor connected to the output of the sampler;
• a ramp delay generator having a first input connected to the pulse repetition interval generator;
• a delay pulse generator connected to the ramp delay generator;
• a delay pulse differentiation capacitor connected to the delay pulse generator and connected to a second input of the sampler.