code: def setPhysicalMinimum(self, edfsignal, physical_minimum):
          
          if (edfsignal < 0 or edfsignal > self.n_channels):
              raise ChannelDoesNotExist(edfsignal)
          self.channels[edfsignal]['physical_min'] = physical_minimum
          self.update_header()
docs: Sets the physical_minimum of signal edfsignal.
  
          Parameters
          ----------
          edfsignal: int
              signal number
          physical_minimum: float
              Sets the physical minimum
  
          Notes
          -----
          This function is required for every signal and can be called only after opening a file in writemode and before the first sample write action.