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Author: Subject: Vacuum meter reading problem!
Salmo
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[*] posted on 3-11-2012 at 09:20
Vacuum meter reading problem!


Hello everybody how would you read this gauge?
It has two scales but I don't understand the small one on the left, why does it end on 1065 mbar? and what pressure does the red pointer point? (it's my ultimate vacuum)
thanks in advance

[Edited on 3-11-2012 by Salmo]

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BromicAcid
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[*] posted on 3-11-2012 at 09:54


Question, that photo you took, is the gauge at atmospheric or is it actually being used to measure vacuum? If it's atmospheric then the long portion of your black needle is pointing toward 760 ish which could be mmHg on the inside scale.



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Salmo
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[*] posted on 3-11-2012 at 10:32


It's atmospheric but It's with the stopper on the suction tube this is without, anyway when it's measuring the ultimate vacuum the black needle goes where the red one is. The red one is adjustable and I placed it on that position to remember what's the ultimate vacuum of the system. Please help me to understand what is my ultimate vacuum pressure and how that scale on the left works..

[Edited on 3-11-2012 by Salmo]

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watson.fawkes
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[*] posted on 3-11-2012 at 11:20


Quote: Originally posted by Salmo  
It has two scales but I don't understand the small one on the left, why does it end on 1065 mbar?
The smaller scale is a quick-read version of the larger one, but in the opposite sign. Note that the sum of the figures on the two scales, where they coincide, is always equal to 1000.

I don't know where the 1065 comes from. I'd imagine that it pertains to some specific application this gauge is for, but I don't know what that is.
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unionised
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[*] posted on 3-11-2012 at 11:29


I wonder if the red one measures atmospheric pressure.

What happens if you put the gauge in a seal-able clear plastic bag and squash it so the pressure rises a bit?
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Salmo
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[*] posted on 4-11-2012 at 07:43


maybe I solved the problem, i think that I have to adjust the black needle position with a screwdriver to the real atmospheric pressure, if you look there is a little plastic stopper. that could be removed, and a small screw on its back. You think I'm right?

[Edited on 4-11-2012 by Salmo]
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Swede
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[*] posted on 4-11-2012 at 08:07


No, the red needle appears manually adjustable, a user set point.

To me, it looks to be an absolute millibar gauge. Standard atmospheric pressure at sea level is about 1013 millibar. As pressure decreases, the black needle rotates CCW towards zero.
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