Hi All,
This question goes out to Bruker users out there with a low temperature
accessory (heat exchanger) in their BVT-3200s. We built a 'home-made'
boxcoil-type heat exchanger which goes down to -120oC with no major
problems. However, we are currently using it without the accessory that
Bruker sells to monitor the level of the lN2 Dewar. This means that one
has to constantly monitor the lN2 level in the Dewar, the gas flow is
not under computer controll, plus bad things can happen if the tank
goes dry.
Anyway, the price for the complete unit is 2,900.00, or 200.00 for the
board (no Dewar, no exchanger, no sensors). I thought that the level
sensors were part of the 200.00 bucks, but they are not - they are
built into Bruker's exchanger. So, the question is, does any one knows
what type of sensors these are? My guess is two resistors in series:
when the first ones comes out of the lN2, there is a change of voltage
(this thing probably puts a constant current on the sensor and measures
a voltage), and you get a warning, and when the second one gets out of
the liquid, the voltage drops even more (the resistance in carbon
resistors grows as they get colder, right?) and shuts down probe
heater. Or something to that effect...
Any ideas? Anyone has seen one of these? With the right values I could
rig it up myself and save me 2,700.00 bucks...
TIA,
Guillermo
+==================-------------- --- -- - - - -
Guillermo Moyna, PhD
Assistant Professor of Chemistry
Department of Chemistry & Biochemistry
University of the Sciences in Philadelphia
600 South 43rd Street
Philadelphia, PA 19104-4495
"The only existing things are atoms and empty space.
All else is mere opinion" - Democritus, 370 B.C.
Office: Griffith Hall 360
Phone: (215) 596-8526
Fax: (215) 596-8543
e-mail: g.moyna_at_usip.edu
WWW:
http://tonga.usip.edu/gmoyna/index.html
http://www.usip.edu/chemistry/faculty/moyna.asp
- - - - -- --- -----------=================+
Received on Mon Mar 08 2004 - 15:57:21 MST