Search found 1312 matches

by John Futter
Mon Mar 01, 2021 5:52 pm
Forum: Vacuum Technology (& FAQs)
Topic: Pirani gauge vs plasma
Replies: 3
Views: 157

Re: Pirani gauge vs plasma

Maciek
It is important that the pirani cannot see the plasma.
active ions arriving will cause heat. The actual exposed thermocouple is extremely small with very low heat capacity.
a couple of righthand bends to isolate the Pirani from the main chamber should sort it
by John Futter
Mon Mar 01, 2021 4:18 am
Forum: Vacuum Technology (& FAQs)
Topic: Help me in my baby steps in the vacuum world.
Replies: 17
Views: 1264

Re: Help me in my baby steps in the vacuum world.

Richard
When we were using Fris grid detectors at work (these are fancy Geiger tubes that position detect) we used Argon and a little 1-2% propane by volume as the quench agent
by John Futter
Mon Feb 15, 2021 1:36 am
Forum: Images du Jour
Topic: House move and cleanup continues
Replies: 2
Views: 263

Re: House move and cleanup continues

Richard
you are bang on
All of those were 2mA max
the 100kV negative I was tempted to keep but!!!
by John Futter
Sun Feb 14, 2021 7:22 pm
Forum: Images du Jour
Topic: House move and cleanup continues
Replies: 2
Views: 263

House move and cleanup continues

We are having a new house built around 100 kms away from where we normally live and a lifetime (almost) of accumulated junk has to go.
So another trailer load to the tip yesterday all very sad!!
spellmans.jpg
by John Futter
Fri Feb 12, 2021 6:16 pm
Forum: Vacuum Technology (& FAQs)
Topic: DIY Turbopump Controller
Replies: 31
Views: 3200

Re: DIY Turbopump Controller

Nicolas It is hard to use linear optos to get volt and current sense across I make sure that there is series impedance then 5 volt TVS diodes across micro I/O pins my comments were directed at some of the other posts where micro derived drive signals are use to drive the half bridge directly a TMP 5...
by John Futter
Wed Feb 10, 2021 4:26 am
Forum: Vacuum Technology (& FAQs)
Topic: Help me in my baby steps in the vacuum world.
Replies: 17
Views: 1264

Re: Help me in my baby steps in the vacuum world.

try to find a manual for the pump

who made it??
it that a sight glass on the opposite side from the pulley?? the oil level should have been visible there
by John Futter
Wed Feb 10, 2021 4:07 am
Forum: Vacuum Technology (& FAQs)
Topic: DIY Turbopump Controller
Replies: 31
Views: 3200

Re: DIY Turbopump Controller

You are doing alright I'm just giving a bit of sage advice learnt from doing wrong it in the first place

ask away and i'll answer
by John Futter
Tue Feb 09, 2021 6:39 pm
Forum: Vacuum Technology (& FAQs)
Topic: DIY Turbopump Controller
Replies: 31
Views: 3200

Re: DIY Turbopump Controller

Nicolas I have looked at your circuit I did not use a micro directly to generate the drive frequency due to the danger of a reset or port hang from it. There is a huge amount of stored energy in a turbo that is why in my diagram it was driven from the 4046 being used as a voltage controlled oscillat...
by John Futter
Sun Feb 07, 2021 6:19 pm
Forum: Items For Sale
Topic: Pumps "R" Us
Replies: 8
Views: 3255

Re: Pumps "R" Us

update Some have been sold I have a selection of high vac pumps for sale Before you all go mad in pushing the buy now I'm in New Zealand so freight is going to cost$$ 1 x edwards E050 air cooled diff pump US$225 each ex mass spec 2 x edwards E02 water cooled diff pumps US$150 each ex mass spec 1 x e...
by John Futter
Sun Feb 07, 2021 2:59 am
Forum: Vacuum Technology (& FAQs)
Topic: Help me in my baby steps in the vacuum world.
Replies: 17
Views: 1264

Re: Help me in my baby steps in the vacuum world.

oils with low vapor pressure are what is needed there are low foaming mineral oils like tonna T25 /238 etc the later figures relate to viscosity.

the above oils are Shell but any oil company expert will cross reference these for you i have done that to Mobil oils but cannot remember the Mobil codes