Teledyne Vacuum Gauge 2002 Manuel d'utilisateur télécharger pdf (Page 21)

Model 2002 page 21

Theory of Operation

SECTION 5

The Model 2002 transducer is comprised of two very different sensors which provide a span of

measurement extending from 1000 Torr down to less than 1x10

-4

Torr. 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 1x10

-4

Torr. The two decade overlap in measurement range is

convenient for smooth transition either descending or ascending in pressure. Both sensors are

small micromachined die that are bonded to a Au coated Al

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 Figure 5.1.

5.1 Piezoresistive Sensor

Electronics board

(contains EEPROM)

Pirani sensor

Piezoresistive

sensor

TO-8

HEADER

Top cap

Cable connector

Tube shell

Figure 5.1

Dual Sensor Embodiment

Preform

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Teledyne Vacuum Gauge 2002 Manuel d'utilisateur Page 21