function volts = adc2volts( counts, sn )
% ADC2VOLTS - Convert Hydra a/d counts to voltage
%
% volts = adc2volts( counts, sn )
%
% Input:
%   counts - array of a/d counts
%   sn     - Hydra serial number as indicated in .ctl file
%
% Output:
%   volts - array of voltages
%
% If the serial number is not recognized, will return volts = 5*counts/65536.
%
% Coefficients calculated in
% /work2/sherwood/proj/GH2001/adv/calc_volts.m

% Chris Sherwood, USGS
% August 17, 2001


if(strcmpi('B45B',sn)|strcmpi('B45',sn)),
  a = 88.5529;
  b = 1.2820e+04;
elseif(strcmpi('B51B',sn)|strcmpi('B51',sn)),
  a = 14.2569;
  b = 1.2819e+04;
elseif(strcmpi('B52B',sn)|strcmpi('B52',sn)),
  a = -29.4892;
  b = 1.2830e+04;
elseif(strcmpi('B59B',sn)|strcmpi('B59',sn)),
  a = -30.8056;
  b = 1.2827e+04;
else
  fprintf(1,'Using default voltage conversion.\n')
  a = 0;
  b = 65536/5;
end
volts = (counts-a)./b;