Balzers Vacuum Gas Pressure Gauge TPR
017 KF Pfeiffer
Nickel filament pirani gauge
The Balzers TPR 017 Vacuum Gauge has
been designed for vacuum measurement of gases in the pressure range from
8 × 10-4 to
1000mBar. The gauge can be operated in connection with the
Vacuum TPG 300 total pressure gauge controller.
Basic principle of Pirani gauge
A conducting wire gets heated when electric current flows
through it. The rate at which heat is dissipated from this wire depends on the
conductivity of the surrounding media. The conductivity of the surrounding media
in turn depends on the density of the surrounding
media (that is, lower pressure of the surrounding media, lower will be its
density). If the density of the surrounding media is low, its conductivity also
will be low causing the wire to become hotter for a given current flow, and vice
- A pirani gauge
chamber which encloses a platinum filament.
- A compensating
cell to minimize variation caused due to ambient temperature changes.
- The pirani
gauge chamber and the compensating cell is housed on a wheat stone bridge
circuit as shown in diagram.
Operation of Pirani gauge
- A constant current
is passed through the filament in the pirani gauge chamber. Due to this
current, the filament gets heated and assumes a resistance which is measured
using the bridge.
- Now the pressure
to be measured (applied pressure) is connected to the pirani gauge chamber.
Due to the applied pressure the density of the surrounding of the pirani gauge
filament changes. Due to this change in density of the surrounding of the
filament its conductivity changes causing the temperature of the filament to
- When the
temperature of the filament changes, the resistance of the filament also
- Now the change in
resistance of the filament is determined using the bridge.
- This change in
resistance of the pirani gauge filament becomes a measure of the applied
pressure when calibrated.
Advantages of Pirani gauge
- They are rugged and inexpensive
- Give accurate results
- Good response to
- Relation between
pressure and resistance is linear for the range of use.
- Readings can be
taken from a distance.
Limitations of Pirani gauge
- Pirani gauge must
be checked frequently.
- Pirani gauge must
be calibrated from different gases