I have used these units(AFS) for a number of years. Customer service and response is very good. Fairly inexpensive and long lasting. I use an Asco cryo solenoid valve and 24vdc supply provided by AFS. Simple, basic and it works.

http://www.afselectronics.com/ln2.html

~Greg

> On Mar 7, 2016, at 6:02 AM, Fred Martin Kaaby <[log in to unmask]> wrote:
> 
> 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
> [log in to unmask]