Cheapest possible system to check dry shipper would be a wooden stick lowered into the shipper then taken out and exposed to moist air. Condensation would indicate a cold zone...
Second cheapest option is a red LED on a pair of long thin wires. If it changes to green as it dips into the dewar, again- it is cold in there. The change will be partial depending on the actual temperature. Please note this only works with inorganic LEDs. If you crave precision and actual numbers, then you should invest a dollar or two in a type K thermocouple. It is good down to -200 C which is lower than LN2 temperature. These are on ebay and Amazon for a few bucks. A few more bucks will get you a thermometer body with the right connector, or you can use a multimeter and recall that the voltage change should be about 41 microcolts per degree C. You can calibrate your system in LN2 and ice or boiling water to get the correct thermal coefficient and offset. Just don't forget to use the same connection and instrument all the time since the reference junction will change if you change the setup. As to re-evacuating the dewar - this varies depending on how your particular device is constructed. Some have a 'nipple' style valve, others have a needle style valve and some are permanently welded shut... it's not obvious that your mechanics shop will have the requisite vacuum connector to service your shipper. We used to send ours to manufacturer for reconditioning. Best of luck, Artem On Fri, Oct 18, 2024, 20:23 Pedro Matias <mat...@itqb.unl.pt> wrote: > Dear All, > > I'm looking for a low temperature measuring system to check our dry > dewars, preferably one that is not very expensive. Any recommendations ? > > Also, I was told that it is possible to regenerate the vacuum in those > vessels. Does anybody have any experience with this? If so, how can it > be done? > > Thanks in advance, > > Pedro Matias > > -- > Industry and Medicine Applied Crystallography > Macromolecular Crystallography Unit > ___________________________________ > Phones : (351-21) 446-9100 Ext. 1669 > (351-21) 446-9669 (direct) > Fax : (351-21) 441-1277 or 443-3644 > > email : mat...@itqb.unl.pt > > > http://www.itqb.unl.pt/research/biological-chemistry/industry-and-medicine-applied-crystallography > http://www.itqb.unl.pt/labs/macromolecular-crystallography-unit > > Mailing address : > Instituto de Tecnologia Quimica e Biologica António Xavier > Universidade Nova de Lisboa > Av. da República > 2780-157 Oeiras > PORTUGAL > > ITQB NOVA, a great choice for your PhD > https://youtu.be/de6j-aaTWNQ > > Master Programme in Biochemistry for Health > https://youtu.be/UKstDCFjYI8 > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a > mailing list hosted by www.jiscmail.ac.uk, terms & conditions are > available at https://www.jiscmail.ac.uk/policyandsecurity/ > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
