Method of measuring and controlling the level of liquid in a container

Claim 1

A method of measuring and controlling the level of an elevated temperature liquid in a container, said method comprising: converting to digital form the electrical voltage signal outputs of a plurality of temperature sensing means located at spaced elevations on a wall of said container above and below the expected level of liquid therein, said electrical signal outputs being indicative of the temperature profile along said wall due to the presence of liquid in the container; periodically scanning the converted signals of the temperature sensing means in sequence with respect to the location of said sensing means on the wall of the container; after converting the signal outputs to digital form, selecting as reference signals those converted signals greater than a predetermined threshold signal value K corresponding to thermal radiation of the liquid material entering the container and to extraneous electrical noise; determining the uppermost sensing means below the liquid level in the container by locating the uppermost pair of adjacent sensing means having reference signals greater than K and in which the upper sensing means of said pair has a converted signal value at least greater than seventy percent (70%) of the converted signal value of the lower sensing means in said pair, the upper sensing means in said pair being designated as n and the converted signal value of said upper sensing means being designated as Sn; calculating a fraction F of the spacing between the sensing means n and the next above sensing means n-1 at which the liquid level is estimated to lie, said fraction being a function of the converted signal value Sn-1 of the sensing means n-1; calculating the location of the measured liquid level in the container from n and F; and controlling addition and withdrawal of liquid to and from the container based on said measured liquid level.

Claim 2

A method of measuring and controlling the level of an elevated temperature liquid in a container, said method comprising: converting to digital form the electrical voltage signal outputs of a plurality of temperature sensing means located at spaced elevations on a wall of said container above and below the expected level of liquid therein, said electrical signal outputs being indicative of the temperature profile along said wall due to the presence of liquid in the container; periodically scanning the converted signals of the temperature sensing means in sequence with respect to the location of said sensing means on the wall of the container; after converting the signal outputs to digital form, selecting as reference signals those converted signals greater than a predetermined threshold signal value K corresponding to thermal radiation of the liquid material entering the container and to extraneous electrical noise; determining the uppermost sensing means below the liquid level in the container by locating the uppermost pair of adjacent sensing means having reference signals greater than K and in which the upper sensing means of said pair has a converted signal value at least greater than seventy percent (70%) of the converted signal value of the lower sensing means in said pair, the upper sensing means in said pair being designated as n and the converted signal value of said upper sensing means being designated as Sn; calculating a fraction F of the spacing between the sensing means n and the next above sensing means n-1 at which the liquid level is estimated to lie, said fraction being a function of the converted signal value Sn-1 of the sensing means n-1; calculating the location of the measured liquid level in the container from n and F; and controlling addition and withdrawal of liquid to and from the container based on said measured liquid level.