gEGU.py

#!/usr/local/bin/python
#
#                               Copyright 2002
#                                     by
#                        The Board of Trustees of the
#                     Leland Stanford Junior University.
#                            All rights reserved.
#

__facility__ = "Online"
__abstract__ = "Classes for handling raw/engineering unit (EGU) oconversions"
__author__   = "R. Claus <Claus@SLAC.Stanford.edu> SLAC - GLAST LAT I&T/Online"
__date__     = ("$Date: 2005/04/13 03:28:48 $").split(' ')[1]
__version__  = "$Revision: 2.4 $"
__release__  = "$Name: R04-12-00 $"
__credits__  = "SLAC"

import LATTE.copyright_SLAC
from math import *


class GEGU(object):
  """\brief Base class for raw/engineering unit conversions.

  """
  def __init__(self, units):
    self.__units  = units

  def egu(self, value):
    """Overloadable method for converting raw units to engineering units

    \param value Value in raw units.

    \return Engineering units value after the conversion.

    """
    return value

  def raw(self, value):
    """Overloadable method for converting engineering units to raw units

    \param value Value in engineering units.

    \return Raw value after the conversion.

    """
    return value

  def units(self):
    """Method for returning the units string

    \return Units string value.

    """
    return self.__units


class GEGU_linear(GEGU):
  """\brief EGU class for performing linear conversions.

  """
  def __init__(self, slope, intercept, units=""):
    """Initialize a raw/EGU linear conversion object.

      \param slope     Number of engineering unit counts per raw value tick
      \param intercept Offset in units of the engineering unit
      \param units     The engineering units name, e.g. 'cm'

    """
    assert slope, "GEGU_linear.__init__: slope argument cannot be zero"
    GEGU.__init__(self, units)
    self.__slope     = slope
    self.__intercept = intercept

  def egu(self, rawValue):
    """Convert a value in raw units to engineering units

    \param rawValue Value in raw units.

    \return Engineering units value after the conversion.

    """

    # Compensate for some pseudo quantities (like PSD_TEM_0)
    # where the rawValue may be received as a large positive
    # value although it is negative.
    if rawValue >= (1 << 31L):
      rawValue = rawValue - (1 << 32L)

    return rawValue * self.__slope + self.__intercept

  def raw(self, eguValue):
    """Convert a value in engineering units to raw units

    \param eguValue Value in engineering units.

    \return Raw value after the conversion.

    """
    return int(round((eguValue - self.__intercept) / self.__slope))

class GEGU_poly3(GEGU):
  """\brief EGU class for performing 3rd degree polynominal conversions.

  """
  def __init__(self, coeff0, coeff1, coeff2, coeff3, offset, units=""):
    """Initialize a raw/EGU linear conversion object.

    \param slope     Number of engineering unit counts per raw value tick
    \param intercept Offset in units of the engineering unit
    \param units     The engineering units name, e.g. 'cm'

    """
#    assert slope, "GEGU_linear.__init__: slope argument cannot be zero"
    GEGU.__init__(self, units)
    self.__coeff0 = coeff0
    self.__coeff1 = coeff1
    self.__coeff2 = coeff2
    self.__coeff3 = coeff3
    self.__offset = offset

  def egu(self, rawValue):
    """Convert a value in raw units to engineering units

    \param rawValue Value in raw units

    \return Engineering units value after the conversion.

    """
    return self.__coeff0 + self.__coeff1*(rawValue-self.__offset) + self.__coeff2*(rawValue-self.__offset)**2 + self.__coeff3*(rawValue-self.__offset)**3

  def raw(self, eguValue):
    """Convert a value in engineering units to raw units

    \param eguValue Value in engineering units.

    \return Raw value after the conversion.

    """
    return 0


class GEGU_thermistor(GEGU):
  """\brief EGU class for performing thermistor conversions.
  
     Actual equation is:  R = (C1 / Counts) + C0
     
     Temp (deg C) = C2 * ln(R) + C3
     
     Nominal C0 = - 1.020 E5
     Nominal C1 =   4.096 E8
     
     Fitted from (-40,80 degree) thermistor data from YSI.  30K ohm column (http://www.ysi.com/extranet/TEMPKL.nsf/447554deba0f52f2852569f500696b21/617d4fec8189026885256a03005d500a/$FILE/R_vs_T%20449XX.xls)
     Fitted C2 = - 20.319
     Fitted C3 =  234.69
     

  """
  def __init__(self, coeff0, coeff1, coeff2, coeff3, units=""):
    """Initialize a raw/EGU conversion object.

    \param coeff[0-3] One of the coefficients of the function.  See function doc
    \param units     The engineering units name, e.g. 'cm'

    """
    GEGU.__init__(self, units)
    self.__coeff0 = coeff0
    self.__coeff1 = coeff1
    self.__coeff2 = coeff2
    self.__coeff3 = coeff3

  def egu(self, rawValue):
    """Convert a value in raw units to engineering units

    \param rawValue Value in raw units

    \return Engineering units value after the conversion.

    """
    if rawValue == 0:   # protect divide by zero
      rawValue = 1
    R = (self.__coeff1 / rawValue) + self.__coeff0
    T = (self.__coeff2 * log(R)) + self.__coeff3
    return T

  def raw(self, eguValue):
    """Convert a value in engineering units to raw units

    \param eguValue Value in engineering units.

    \return Raw value after the conversion.

    """
    return 0


class GEGU_rtd(GEGU):
  """\brief EGU class for performing RTD (Resistive Temp Device) conversions.
  
     Actual equation is:  
      
      C = ( R/(R+C0) - 1/(C2) ) * C1
      
                  C0 (C C2 + C1)  
      R =      - -----------------  
                 C C2 - C1 C2 + C1  
               
      Temp = ( R + C4 ) / C5
      
      Nominal C0 = 1820
      Nominal C1 = 4096  (Exact)
      Nominal C2 = 3
  
      Fitted from +/- 100 degree data from 0118MF literature from Goodrich (manufacturer)  
      Fitted C3  = - 1994.5
      Fitted C4  = 7.9051      

  """
  def __init__(self, coeff0, coeff1, coeff2, coeff3, coeff4, units=""):
    """Initialize a raw/EGU linear conversion object.

    \param coeff[0-4] One of the coefficients of the function.  See function doc
    \param units     The engineering units name, e.g. 'cm'

    """
    GEGU.__init__(self, units)
    self.__coeff0 = coeff0
    self.__coeff1 = coeff1
    self.__coeff2 = coeff2
    self.__coeff3 = coeff3
    self.__coeff4 = coeff4

  def egu(self, rawValue):
    """Convert a value in raw units to engineering units

    \param rawValue Value in raw units

    \return Engineering units value after the conversion.

    """
    R = - self.__coeff0 * \
          ( ((rawValue*self.__coeff2) + self.__coeff1) / \
            ((rawValue*self.__coeff2) + self.__coeff1*(1-self.__coeff2)) )
    T = ( R + self.__coeff3 ) / self.__coeff4
    return T

  def raw(self, eguValue):
    """Convert a value in engineering units to raw units

    \param eguValue Value in engineering units.

    \return Raw value after the conversion.

    """
    return 0

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