docs: def sampling_volume(self, val):
          """Sets sampling volume."""
          if self.instrument == "Vectrino" and type(val) is float:
              if val == 2.5:
                  self.pdx.SamplingVolume = 0
              elif val == 4.0:
                  self.pdx.SamplingVolume = 1
              elif val == 5.5:
                  self.pdx.SamplingVolume = 2
              elif val == 7.0:
                  self.pdx.SamplingVolume = 3
              elif val == 8.5:
                  self.pdx.SamplingVolume = 4
              else:
                  raise ValueError("Invalid sampling volume specified")
          elif val in range(5):
              self.pdx.SamplingVolume = val
          else:
              raise ValueError("Invalid sampling volume specified")