%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%    Hm7.m  -  B-H interpolation routine
%              Used by joint.m
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function y = Hm7(Btx)
% B-H values that follow are valid for M-7, 0.014 in. ESS
B=[0 20 30 40 50 60 65 70 80 85 90 95 100 105 110 115 ...
   117 120 125 130 140 210 ]*1000;
H=[ 0 0.4 0.51 0.61 0.71 0.80 0.85 0.90 1.04 1.18 1.35 1.7 2.4 ...
   4.4 9.0 18 26 100 400 1000 10000 100000 ];
% Activate to plot B-H curve
% m=120; plot(H(1:m),B(1:m)); grid; pause; % Linear plot
% m=21; semilogx(H(2:m),B(2:m));grid; pause; % Semilog plot
n=length(B); k=0;
if Btx==0; k=-1; y=0; end
if Btx<0; k=-1; y=0; disp('WARNING - Btx < 0, Htx = 0 returned'); end
if Btx>B(n); y=H(n); k=-1; disp('CAUTION - Beyond B-H curve'); end
for i=1:n
if k==0 & (Btx-B(i))<=0; k=i; break; end
end
if k>0;
y=H(k-1)+(Btx-B(k-1))/(B(k)-B(k-1))*(H(k)-H(k-1));
else;
end