Please click your language flag. Bitte Sprachflagge klicken.


Information - Help 
ID = 37085
United States of America (USA)
Brand: Westinghouse El. & Mfg. Co. - see also Canadian W.
Tube type:  Ionisation or Vacuum Gauge 
Identical to WL765

Base UX-Base (4 Pins (2 thick, USA 1924, UX)
Was used by Technology / Measurement

Pirani vacuum gauge.

The filament inside the bulb is connected to a Wheatstone bridge circuit. Heating due to the current flowing in it depends upon the covection-cooling due to the molecules of gas still present. The lower the gas pressure, the higher the temperature of the filament. The vacuum can be then measured by the bridge unbalance due to the temperature coefficient of the filament.

WL765: Private collection
Emilio Ciardiello

More ...

from Just Qvigstad

Forum contributions about this tube
Threads: 1 | Posts: 3
Hits: 1282     Replies: 2
a peculiar device
Wolfgang Holtmann

Lately, on a meeting with radiofriends, someone came up with this interesting glass tube:

On the bottom we see two pins leading to a sort of heater wire. The measured resistance is appr. 5 Ohms. The writing is hardly to identify. With the use of a magnifier lens one can make up:

APC-8065 CELL,  110V,   ITALY

The first idea was, could it be a so called Vacuum-Gauge? No, because a third connection  is missing!

Any suggestions are welcome....



Emilio Ciardiello

Likely it is a Pirani vacuum gauge. This kind of sensor is based upon the convection cooling of a wire, heated by a current flowing in it, by molecules of rarefied gas inside the bulb. The final temperature gives an indication of the vacuum reached.

The sensor is used in a bridge circuit, sometimes with a second sealed sensor as reference, which supplies current to the filament and returns at the same time an unbalance due to the resistance value corresponding to the vacuum.

Look as example at WL765 or at R1111.


Wolfgang Holtmann

Many thanks Emilio for the explanations!


Credit to Wikipedia for the depicted diagram.

Regards, Wolfgang

End of forum contributions about this tube

You reach this tube or valve page from a search after clicking the "tubes" tab or by clicking a tube on a radio model page. You will find thousands of tubes or valves with interesting links. You even can look up radio models with a certain tube line up. [rmxtube-en]