Modified tdr method and apparatus for suspended solid concentration measurement

A method for measuring a suspended solid concentration of a suspension by using the principle of time domain reflectometry to measure a reflected waveform with a concentration measuring apparatus which comprises a TDR sensing waveguide, a temperature sensor, a time domain reflectometer connected to the TDR sensing waveguide, and a data acquisition system connected to the time domain reflectometer and the temperature sensor, wherein the TDR sensing waveguide comprises a set of probing conductors, a coaxial cable, and a probe adapter connecting the coaxial cable with the probing conductors, and the method comprises steps of:

• submerging the probing conductors in the suspension;
• using the temperature sensor to measure a temperature of the suspension;
• analyzing the reflected waveform to determine a TDR travel time;
• and
• using a predetermined temperature-corrected relationship between the TDR travel time and the suspended solid concentration to determine the suspended solid concentration of the suspension, and the step of determining the TDR travel time further comprises steps of:
• identifying a first part of the reflected waveform from the impedance discontinuity interface of the coaxial cable and using a vertex or other stable characteristic points in the first part of the reflected waveform as a temporal reference point of an electromagnetic wave travel time;
• identifying a second part of the reflected waveform from the distal end of the TDR sensing waveguide and using a vertex or other stable characteristic points in a derivative of the second part of the reflected waveform to define an arrival time of an electromagnetic wave travel time;
• and
• calculating a time difference between the arrival time and the temporal reference point as the TDR travel time.