4.Theory of Operation
The 2002s transducer tube is comprised of two very different sensors which provide a span of measurement extending from 1000 Torr down to less than 1 ⋅ 10-4Torr. The piezoresistive device is a direct force sensor which provides pressure indication from 1000 Torr down to less than 1 Torr. The thin film Pirani device is a thermal conductivity sensor that provides pressure indication from 100 Torr down to less than 1 ⋅ 10-4Torr. The two decade overlap in measurement range is convenient for smooth transition either descending or ascending in pressure. Both sensors are small micro machined die that are bonded to a Au coated Al2O3 preform (stress-isolation) which in turn is bonded to a TO-8 header. The header is resistance welded into a 316 stainless steel envelope as shown in the Figure 4.1.
4.1.1.
PCB
EEPROM
TO-8
HEADER
PIRANI
PIEZOSENSOR SENSOR
Figure 4.1
HPM-2002-OBEVacuum Gauge | Page 25 of 39 |
