I have been thinking on the same thing but more in the direction of tinkering together something by myself. Here's my thought:

Shopping list (A grand total of under 100 euros):
- Ultrasonic range finder (I personally like "PING" from Parallax)
- Arduino UNO or similar Arduino with Pulse Width Modulation support (No reason to overkill, A Adafruit Tinker 5V would perhaps be good)
- Solenoid valve (12V in this case)
- External 9V and 12V powersupply (from an old computer maybe+)
- Breadboard and some wiring. Remember the solenoid is power hungry so the wiring need to be scaled accordingly! 

In addition you might need:
- External reservoir of LN2 with fitting outlet 
- Swagelok tubing and unions fit for the solenoid and LN2 reservoir

The idea is that the ultrasonic range finder will measure the surface level of the nitrogen real-time. Output a number in which you can relate to when you open or close the solenoid from the LN2 reservoir. 
The LN2 tank will then refill the Gasbench trap. 

The solenoid have to endure -196 degrees Celsius. Standard solenoid valves might not be good enough. Maybe a cryo solenoid from an old GC is fit for this purpose?

I'm curious whether others have thought about or maybe done similar?


Hilsen/Regards
Fred Martin Kaaby




-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Rugh, William
Sent: 5. mars 2016 17:49
To: [log in to unmask]
Subject: [ISOGEOCHEM] Automated Liquid Nitrogen Refill for Gas Bench

I'm looking to purchase an automated refill system for our dual trap dewar on the Gasbench.  So far I haven't found many options other than Teragon of San Francisco.  I would appreciate any suggestions, recommendations or comments.  You can respond to me directly at [log in to unmask]
	Thanks!


William Rugh, Manager
Integrated Stable Isotope Research Facility US Environmental Protection Agency Western Ecology Division
200 SW 35th St. Corvallis OR 97333
541 754-4604
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