Penning Measuring gauge configuration

In summary, Penning pressure gauges are used to determine pressures ranging from approximately 1E-7 to 1 mbar. The Penning gauge is placed outside the recipient and behind a valve to prevent it from being exposed to pressures over 1 mbar. Using a smaller valve may result in higher end pressures due to entrapped particles, but it is difficult to predict the exact increase. The dimensions for the penning gauge and pipes are typically DN40 for the gauge, DN40 or DN16 for the pipe from the gauge to the valve, and DN40 for the pipe from the valve to the recipient. A smaller valve may result in molecules getting trapped inside the pipe, leading to an increase in measured end pressure. However,
  • #1
Ryyder
5
0
We use, among others, Penning pressure gauges for determining pressures (aprox. 1E-7 to 1 mbar (about the same in Torr... for the Americans here ;-) ).
The Penning is placed just outside the recipient, behind a valve to make sure its never in pressures of 1mbar or more.

When using a smaller valve, the measured end pressure is higher (entrapped particles probably?). But the question now is, how to pre-determine how much higher the measured pressure will be due to this effect, without having to measure for each application.

My feeling is that a smaller valve and therefore smaller pipes in front of the gauge, result in relatively more particles being entrapped in the volume of the gauge. But I can't find a good way of approximating the effect.

More general:
* What is the effect a decreased diameter in front of the measurement?

Any thoughts are welcome!
Ryyder
 
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  • #2
No ideas at all? I was thinking it might be due to free path length being a lot more then the length and diameter of the pipe in front of the Penning.

If the inlet to this pipe is made smaller, molecules might get trapped inside the pipe?
 
  • #3
Basically one is measuring the pressure of a vacuum?

Perhaps there is no one here who works with vacuum systems on a regular basis.


How small is small? Or what are typical dimensions?
 
  • #4
Yes, measuring the pressure of the vacuum. And yes, maybe not many people have experience or direct knowledge, could be.

The dimensions are as follows, for two cases (in mm):
* Penning is typically DN40
* Pipe from penning to valve is DN40 or DN16, ~75 mm long
* Valve is DN40 or DN16
* Pipe from valve to recipient (the vacuum) is DN40, ~20 mm long

For the DN16 valve we see a clear increase in end pressure that is measured for the vacuum, even though we know the vacuum itself has the same end pressure (or at least will not change in the order of decades).
 
  • #5
hi ryder..
the penning gauge and the size of the whole are directly linked for certain..ive worked with edwards and leybold gauges many years , no one has ever to my mid actually produced a document to corrulte any results..its the nature of the gauge I am afraid..ill put link to our gauges section if you ley me know ill could possibly geta pdf on sucha unit for you http://www.absolute-vacuum.com/product_gauges.php
 
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Related to Penning Measuring gauge configuration

1. What is a Penning Measuring gauge configuration?

A Penning Measuring gauge configuration is a type of vacuum gauge used to measure the pressure of a gas in a vacuum system. It consists of two electrodes, a magnetic field, and a gas-filled chamber. When a voltage is applied to the electrodes, the resulting ionization of the gas produces a current that is proportional to the pressure of the gas.

2. How does a Penning Measuring gauge configuration work?

The Penning Measuring gauge configuration works by applying a voltage between the two electrodes, creating a magnetic field that ionizes the gas in the chamber. The ionized gas creates a current that is measured by the gauge. The strength of the magnetic field and the pressure of the gas are directly proportional, allowing for accurate pressure measurements.

3. What are the advantages of using a Penning Measuring gauge configuration?

Some advantages of using a Penning Measuring gauge configuration include its ability to measure low pressures (down to 10-10 Torr), its wide range of measurement (10-10 - 10-3 Torr), and its accuracy and repeatability. It also does not require calibration and is not affected by the type of gas being measured.

4. What are the limitations of a Penning Measuring gauge configuration?

One limitation of a Penning Measuring gauge configuration is its sensitivity to magnetic fields. If there are strong magnetic fields present in the system, it can affect the accuracy of the gauge. Another limitation is that it cannot measure pressures above 10-3 Torr, as the ionization current becomes too high and can damage the gauge.

5. How is a Penning Measuring gauge configuration calibrated?

A Penning Measuring gauge configuration is typically calibrated using a known pressure standard, such as a Pirani gauge or a capacitance manometer. The gauge is connected to the standard and readings are compared to determine the accuracy of the gauge. Some gauges also have a built-in calibration feature that allows for easy and quick calibration.

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