/*************************************************************************
 * YSI44031_to_F
 *
 * Conversion routine: Thermistor reading (volts) to degF
 *                     Uses Steinhart and Hart approximation
 * Routine takes 1 argument:
 *   psub->a    - Voltage drop across thermistor (HacE_D1_NMR:SREG)
 *   psub->val  - returns calculated temperature in degrees Farenheight
 *
 ***************************************************************************/

#include        <vxWorks.h>
#include        <types.h>
#include        <dbDefs.h>
#include        <dbAccess.h>
#include        <dbFldTypes.h>
#include        <errMdef.h>
#include        <recSup.h>
#include        <subRecord.h>

float YSI44031_to_F(struct subRecord *psub)
  {
/*constants for Steinhart and Hart equation for YSI44031*/
  float A = 1.0284299584E-3;
  float B = 2.3927781009E-4;
  float C = 1.5591039659E-7;
/*fixed resistor value in voltage divider*/
  float RFIXED = 10000.0;
/*voltage output of voltage reference used as source*/
  float VREF = 10.0;
  float A1,B1,G1,R1,T1;
/*voltage drop across thermistor*/
  float VDROP;

  static unsigned char UDF = TRUE;
  if(UDF)
    {
    psub->udf = FALSE;
    UDF = FALSE;
    }

  VDROP = psub->a;
  psub->val = 0.;

    R1 = ((VDROP/VREF)*RFIXED)/(1-(VDROP/VREF));

    B1=log(R1);
    G1=exp(3*log(B1));
    A1=A+(B*B1)+(C*G1);
    T1=(1/A1)-273.15;
/*now we have centigrade*/
    T1=(T1*1.8)+32;
/*now we have farenheight*/

  psub->val = T1;
  return(0);           
  };