Provided is a melt composition for a heat shrinkable foam structure that includes at least one base polymer and a blowing agent made from at least one heat-activated chemical compound encapsulated by a plurality of polymeric shells. The opening is preferably rectangular in shape, but other shapes may also be used. In the shield cover, a tubular portion which forms a fitting portion for a plug, mounting terminals for a printed circuit board, first contact pieces for a shield member of the plug, and second contact pieces for a case of an apparatus are integrally disposed. The starting position is at 12 o’clock, first shot is 1 o’clock, second shot is 2 o’clock, etc. Each light detector produces a signal indicating an intensity of light received from within the tubular lens and the signals are process to derive a turbidity measurement.