function ctd = getPar(ctd,vvar);

% Post-February 2008
    M = 1.0;
    B = 0.0;
    ConFac = 10111223458.03842;
    Multi_E = 1.0; %outputs PAR in uEinsteins/m^2 sec
    Multi_W = 0.2174; %outputs PAR in Watts/m^2
    offset = -0.15423974;

%calibration factors for Feb 7 2008
%ConFac = 10111223458.03842;
%offset = -0.15423974;

%ctd.Par =  (ctd.(vvar)-offset)*ConFac;  %Jody's version - INCORRECT!
% corrected equation from Ian Beveridge (Jun2010)
ctd.Par = (Multi_E * (10^9 * 10.^(ctd.(vvar)-B/M))/ConFac) + offset; 