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Re: News from Argentina

Posted: Tue Jan 23, 2018 7:03 pm
by Finn Hammer
Roberto Ferrari wrote:
Mon Jan 22, 2018 9:47 pm
Hi Jerry

Good point, thanks!
That one is 100 torr but we have also 10 torr FS.
We will manage to put an elbow or swap positions with the viewport, now at cross lower port.
Roberto,

Please be aware,that the 10 torr FS unit puts out 1mV per Micron of pressure, so that you are at the very far edge of the transducers usefull range.
With fusor pressures around 10-50 Micron, You will be measuring from 10-50mV, not a lot in a noisy environment. A better choice would be a 0.1torr unit, or even a 0.05 torr unit.
With a full scale output of 10V, the latter will still produce a full one volt at 5 Microns, and as such deliver a better resolution.
Another benefit of having a transducer with a FS close to the fusing pressure is, that it is able to deliver useful output at a couple of decades higher vacuum, prior to letting the deuterium into the fusor, the 10 torr unit will "bottom out" long before that.
In short, with a 10 torr unit, you will miss most of the action you get from the diff. or turbo pump, since it's output has fallen to 1mV at a pressure of 1 Micron.

Just some thoughts I did before choosing my Baratrons, both 0.05 torr FS. (One of which, by the way, clearly is marked, that it must be mounted horizontally to read correctly, go figure)

Cheers, Finn Hammer

Re: News from Argentina

Posted: Tue Jan 23, 2018 8:22 pm
by Roberto Ferrari
Hi Finn
Thanks for bringing that issue. You are right.
We already had those Baratrons for other purposes. Now on eBay seems to be a restriction for exporting those devices, so we feel unsafe buying one and sending to our country.
With regard to high vacuum readings we already have a Bayard-Alpert gauge.

Re: News from Argentina

Posted: Tue Jan 23, 2018 11:44 pm
by Dennis P Brown
Finn is correct. My 10 torr unit is very good and accurate from 10 torr down to 150 microns but is very difficult to use below that (never been able to get a stable calibration in that extreme low end.) I use a very precise thermocouple type gauge and it works from 0.150 microns up to 50 microns (Calibrated both extreme's and agrees closely between) and is fine for up to 200 microns (though not too accurate in that upper range.) Finding solutions for pressure is not easy using e-bay surplus but can be done. Of course, I use an ion gauge below 0.1 micron.

Re: News from Argentina

Posted: Thu Jan 25, 2018 11:49 am
by Roberto Ferrari
Finn and Dennis,
Thanks for your advice.
We are getting a loaned capacitance manometer 1 torr FS.
As soon as installed, we will report results.