Research on HV to UHV vacuum gauge and controller build (Amateur scale)

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In summary, the person found a controller unit (TM120) and gauge tubes (TR112) for a High Vacuum system and attempted to find schematics or pinouts for either device, but was unsuccessful. They contacted the manufacturer and was sent a catalog of new controllers, which discontinued support for the legacy products. They are trying to find another controller and gauge tube that is compatible with the unit.
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How did you find PF?: Looking for Circuits on Pirani Gauges

I am in the process of building a High Vacuum system and obtained an outdated Pirani Gauge controller TM120 on ebay. The unit is from Leybold Heraeus company and is built with quality. I contacted them on information on the manuals and on the Gauge tube itself. They sent me various pdf files but none provided a schematic or any pinouts on either the controller unit (TM120)or the Gauge Tubes (TR112).

Tried searching on ebay on the Gauge tubes Tr111 or Tr112 but could not find any. I am assuming that it might be possible to use an existing gauge tube from a different manufacturer to the controller and make it work. Tried to contact Leybold to ask if this were possible and they sent me a current catalog of new controllers (unsupportive of legacy products and pushing new ones is their biz motto) . They said that both units are obsolete etc.

It is a very nice controller and it would be a shame not to use it considering I purchased from ebay at a very cheap price (buyer beware of obsolete electronics not supported by manufacturers).

My thoughts are that Pirani Gauges are not that complicated and looking at the circuit it provides a 12V dc regulated power output with a set of precision resistors in the controller. The pdfs provided on the Tr111/Tr112 shows a possible Wheatstone bridge circuit in the gauge head with a separated vacuum sense tube that plugs into the overall gauge head.

So I am trying to locate other brands with the same type of configuration to determine the pinout and the possible substitution of other gauge tube sensors from other manufacturers to be used with the unit. It is a passive unit and not active since all the voltages and controlling circuits are in the controller. If anyone knows of or has retrofitted or modified a pirani gauge such as this or has additional information it would be greatly appreciated!

Looking forward to any feedback on the subject. I provided the manual that Leybold sent me on the gauge tubes. I also have the manual on the controller unit TM120 if anyone is interested.


  • +TR111-TR112 Manual.pdf
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I have learned that Leybold discontinued the Controller TM120 and the Gauge Tube Tr112 because the Gauge tube heater wire would break easily even when placed on the shelf very fragile. So has anyone ever created or modified a pirani tube to work on other manufactured controllers? Any ideas or thoughts?

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