Vaccum pump control Help please

Thread Starter

Alvin0119

Joined Dec 13, 2018
1
Hi, I'm after a circuit design for a vacuum pump control, I need it to pull 4hg with pressure peaks of up to 10hg , unsure on how to design it, very new to this. All help is appreciated. Thanks in advance.
 

wayneh

Joined Sep 9, 2010
17,153
We'll need a lot more details and context. Why are you doing this - what't the situation and the goal? What are the details of the pump such as voltage, current requirements? Do you need a feedback loop, so that something about the pump operation depends on a vacuum sensor?
 

LesJones

Joined Jan 8, 2017
3,509
I would guess it some unspecified units of height of a column of mercury. (But I think you will have also made the same guess and I also think you will have guessed the same as me that the unit of distance is mm,) I am surprised that his teachers have not drummed into him the importance of specifying units rather than just a number,

Les.
 

jpanhalt

Joined Jan 18, 2008
11,088
I would guess it some unspecified units of height of a column of mercury. (But I think you will have also made the same guess and I also think you will have guessed the same as me that the unit of distance is mm,) I am surprised that his teachers have not drummed into him the importance of specifying units rather than just a number,

Les.
There is an important difference between torr (mm Hg ) and microns -- at least in my experience. The former can use a simple TC (thermal conductivity) gauge. The latter needs something like a vacuum tube ("ionization") gauge.
 

jpanhalt

Joined Jan 18, 2008
11,088
Vacuum units are a strange mashup of related units. Pascal is the offical SI unit but most of the US industrial (high-vacuum physics and engineering) high vacuum units display in mTorr (millimeter of Hg).
In my experience years ago, a Torr was a mm of Hg, and we commonly expressed the pressure as an exponent of Torr, e.g., 10^-6 Torr. Didn't use the "mashup" of mTorr.
 

joeyd999

Joined Jun 6, 2011
4,477
Vacuum units are a strange mashup of related units. Pascal is the offical SI unit but most of the US industrial (high-vacuum physics and engineering) high vacuum units display in mTorr (millimeter of Hg) or Torr.
https://www.mksinst.com/product/Category.aspx?CategoryID=525
Even worse: many commercial/scientific instruments use mbar as the basic unit of vacuum measure.

And the operators/technicians/scientists don't even refer to the units in communications:

"Hey, Jim, what's the vacuum level right now?"

"Oh, about ten to the minus five..."

Simply maddening.
 

nsaspook

Joined Aug 27, 2009
8,774
In my experience years ago, a Torr was a mm of Hg, and we commonly expressed the pressure as an exponent of Torr, e.g., 10^-6 Torr. Didn't use the "mashup" of mTorr.
Normal US SEMI practice is to use the mTorr (old school microns) mashup with rough vacuum as it gives nice scaled (0 to ~1000 max) numbers on a display gauge in the pumps operational range and then switch to exponent notation in high vacuum where the decade is the main scale of vacuum quality.

2017-06-21_10-29-51.jpg
 
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