公开(公告)号：US3555880A

公开(公告)日：1971-01-19

申请号：US3555880D

申请日：1967-04-12

申请人： INDUSTRIAL NUCLEONICS CORP

发明人： MENIUS ARTHUR C JR ,  BENTLEY HARRY THOMAS

IPC分类号： G01N9/00

CPC分类号： G01N9/002 ,  G01N2009/004

摘要： DISCLOSED IS A SYSTEM FOR MEASURING THE DENSITY OF A LIQUID IN RESPONSE TO CHANGES IN THE RESONANT FREQUENCY OF A PIEZOELECTRIC CRYSTAL. FIRST AND SECON PIEZOELECTRIC CRYSTALS ARE POSITIONED IN PROXIMITY TO EACH OTHER AND APPROXIMATELY AT THE SAME DEPTH BELOW THE LIQUID SURFACE. ONE OF THE CRYSTALS IS LOADED BY THE LIQUID BEING MONITORED WHILE THE SECOND CRYSTAL IS POSITIONED IN A BODY OF REFERENCE FLUID THAT IS COUPLED WITH THE LIQUID BEING MONITORED SO THAT THE DIFFERENCE IN RESONANT FREQUENCIES OF THE CRYSTALS IS INDICATIVE ONLY OF THE DENSITY OF THE MONITORED LIQUID. THE DIFFERENCE IN THE RESONANT FREQUENCIES OF THE TWO CRYSTALS IS DERIVED BY DRIVING THE CRYSTALS WITH OSCILLATORS, THE OUTPUTS OF WHICH FEED A MIXER DRIVES A FREQUENCY METER.