MASS MEASUREMENT INTO A FREEZE-DRYER

• Abstract:

  This paper deals with two scales that are conceived to operate inside a freeze-dryer, where the environmental conditions (temperature down to -80 ºC and pressure down to 0.5 Pa) prevent traditional mass transducers to be employed. One scale is based on a parallel-electrode capacitor, whose capacity depends on the position of a moving electrode that, in turn, depends on the unknown mass. The capacity change is converted into a frequency change by means of an oscillator circuit. The second scale, which is still under development, is based on electrostatic levitation. A fixed metallic plate is divided into four sectors connected to a high voltage generator. The resulting electric field is used to levitate a moving metallic plate which carries the unknown mass. A prototype of the capacitor-based scale has shown an uncertainty of a few tenths of grams in the range of 0 g to 250 g.
• Keywords:

  mass measurement, capacitance transducers, lyophilisation systems
• Download:

  IMEKO-WC-2000-TC3-P062.pdf
• DOI:

  _unreg_wc-2000.062

Event details:

• IMEKO TC:
• Event name:

  XVI IMEKO World Congress
• Title:

  Measurement - Supports Science - Improves Technology - Protects Environment ... and Provides Employment - Now and in the Future

• Place:

  Vienna, AUSTRIA
• Time:

  25 September 2000 - 28 September 2000