/* bolometer1:
   Calculate the input power from the measured voltage, by solving the
   quadratic equation.

   Input: The measured voltage [mV]
   Output: The calculated power [mW, dBm]

   Version 2013-06-07
   
 * ----------------------------------------------------------------------------
 * "THE BEERWARE LICENSE" (Revision 44):
 * Dr. Rolf Freitag (rolf dot freitag at email dot de) wrote this file.
 * As long as you retain this notice you can do whatever
 * the GPL (GNU Public License version 3) allows with this stuff.
 * If you think this stuff is worth it, you can send me money via
 * paypal, and get a contribution receipt if you wish, or if we met some day
 * you can buy me a beer in return.
 * ----------------------------------------------------------------------------      
   
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

// solution of the quadratic equation
long double
calc_x1 (long double a, long double b, long double c)
{
  long double x1 = 0;
  x1 = ((-b) + (sqrtl (powl (b, 2) - (4 * a * c)))) / (2 * a);
  return x1;
}

int
main (int argc, char *argv[])
{
  long double x = 0, y = 0, z = 0;
  char **endptr = &(argv[1]) + 10;

  if (argc < 2)
    return (-1);
  y = strtold (argv[1], endptr);          // mV, input
  x = calc_x1 (-9.762e-6, 7.232e-2, -y);  // with a and b from the calibration
  //z=10*logl(x)/logl(10.0); // dBm
  z = 10 * log10l (x);       // dBm
  printf ("At %.2Lf Millivolt the Power is %.1Lf mW = %.1Lf dBm.\n", y, x, z);
  return (0);
}