Try this:
function [tank_volume mA_points fuel_level mA_reading] = get_tank_volume(tank_diameter, tank_length, sensor_read)
% Calculate the volume of the tank
tank_volume = pi * (tank_diameter/2)^2 * tank_length;
vol_temp = 0:0.1:1;
vol_temp = vol_temp .* tank_volume; % Now your volume is divided into 10% increments
mA_points = linspace(4,20,numel(vol_temp)); % your mA points divided in to same number of volume increments
% Now fit a straight line through the volume and mA points to get the line-equation
coeffs = polyfit(vol_temp, mA_points, 1);
mA_slope = coeffs (1);
mA_intercept = coeffs (2);
% Now if you have the mA reading from the sensors
% then you can get the current fuel level by:
fuel_level = (sensor_read - mA_intercept)/mA_slope;
mA_reading = sensor_read;
% Instead if you have the fuel level reading and would like to
% get the equivalent mA reading, uncomment the below 2 expression
% fuel_level = sensor_read;
% mA_reading = (mA_slope * sensor_read) + mA_intercept
end
Once you get the required variable, you can plot the level as a rectangle with curved edges to resemble the tank.
tank_diameter=10;tank_length = 100; fuel_level = 45;
h=figure(1);
clf;
hold on;
% The first rectangle will draw the tank
rectangle('Position',[1 0 tank_diameter tank_length],'Curvature',0.5);
% The second rectangle will fill the tank based on the reading
% make sure to keep the curvature value same between the two rectangles for it to look good
rectangle('Position',[1 0 tank_diameter fuel_level],'Curvature',0.5,'FaceColor','b');
ylabel('Fuel level (L)');
ax=gca;ax.XTick=[];ax.XColor='none';
daspect([1 1 1]);
Hope this helps.
