Hi Dachun,

If you can't reach -120 and the dewar is filled with LN, it could be a bad
temperature sensor. These fail regularly. Just replace the sensor. I buy
male and female crimps so I can rapidly swap them out without having to
solder to save time. They fail regularly when in heavy use. 

Another problem could be the pressure in the LN tank is too high so you
can't fill the dewar and it spills out instead. Less than 22 psi usually
works. After trying to fill and failing, check the LN2 level in the dewar,
if it is low, this could be the problem.

Matt

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Dachun Zhang
Sent: Monday, September 23, 2013 3:42 PM
To: [log in to unmask]
Subject: [ISOGEOCHEM] L-N2 sensor of Kiel device

Dear Isotopers:

I have difficulty to find a L-N2 sensor position to satisfy both -120 C and
-170 C for our Kiel device. I moved up and down the sensor mm by mm, still
couldn't find a good spot, either too high or too low. A defect sensor, or
thermostat or other reason?

I saw the machine trying three times to get to -120C. It might work if I can
set it to try four or  five times. Is that recommended? If so, how can I
change the setting?

Thanks for help.

Dachun Zhang
ESS Dept, UCI