- Joined
- Nov 12, 2002
- Location
- Rootstown, OH
I'm sharing the raw, unparsed data I've collected so far. I'd like to seek your feedback. Feedback can be:
- anything this data makes you think
- any questions it may raise in your mind
- additional situations you'd like to see tested
- suggestions
- criticism
Please note that before this is written up I'll make pretty graphs and present it nicely - this is raw prior to any editing, in the interest of ensuring I cover the right bases and gather whatever data any of you may consider relevant.
Check it out, and reply if you like.
Some of the data in this first post will need to be captured again, due to recalibration of the thermometer.
This is the initial control test, pot mounted, probe mounted to copper hot plate, heat load turned off - this reflects idle temperature and is a relatively consistent 14C across the sample range which was about 30 seconds:
This was my initial test. No heat load still, but going from idle down to -100C. This reflects how temperature responds at the probe, with LN2 applied to the pot. In about 6 minutes and 40 seconds, the probe went from 15C to -100C with consistent pouring to keep it near full:
My next test had a data gathering error - the Tenma 72-7712 software program which creates an excel spreadsheet and a graph, sometimes crashes. It crashed, and no data was gathered. This test was with a heat load applied, bringing the pot from 15C down to full pot, wherever that ended up on the temp gauge. This was abandoned before full pot was reached, due to the software error.
My next test was pulling the pot temperature down to -115C, then beginning to collect data, until full pot was reached:
After full pot was reached, I recalibrated the probe to -195.5C when maintaining full pot with no heat load - this doesn't matter, except all of these tests will be performed again, because I recalibrated the probe again after testing (based on dipping the probe directly into LN2, and setting the probe to read just below -195.5C). The beginning of this graph reflects a full pot with no heat load and temps consistently at ~-195C. When temps begin to rise, that reflects powering the heat load on, with consistent pouring to maintain full pot without overflow. When the graph levels out again, that reflects equilibrium - heat load fully powered, pot maintained at full without overflow. It held the probe to -178C in this state. Then I stopped maintaining the pot - when temps began to rise reflects when all LN2 was boiled off and was no longer audible. Even with barely any LN2 left in the pot, the temp probe remained stable at that -178C equilibrium point until the LN2 was gone.
This test reflects attempting to maintain a temperature of -115C with a heat load applied, with beginning recording when the probe hit -120C from a small splash of LN2 just prior to recording. From 0 minutes to 1.5 minutes, the temp was swinging high and low as I got control of the pot. From minute 2 to minute 6, approximately 4 minutes, I maintained temps to the best of my ability - constant maintenance with absolute concentration - results were no warmer than -113c or colder than -119C during this period. Realistically, to control temps to this degree I would have needed someone else to run the bench while I maintained the pot, and the heat load would have needed to remain constant as it was throughout this entire test. After the 6 minute mark of the test, I slammed the pot to see how it would respond. This test also represents a fully frosted pot under real benching conditions (the pot has been cold, may have warmed up a bit, then frosted again - this tends to affect how the pot responds to LN2):
- anything this data makes you think
- any questions it may raise in your mind
- additional situations you'd like to see tested
- suggestions
- criticism
Please note that before this is written up I'll make pretty graphs and present it nicely - this is raw prior to any editing, in the interest of ensuring I cover the right bases and gather whatever data any of you may consider relevant.
Check it out, and reply if you like.
Some of the data in this first post will need to be captured again, due to recalibration of the thermometer.
This is the initial control test, pot mounted, probe mounted to copper hot plate, heat load turned off - this reflects idle temperature and is a relatively consistent 14C across the sample range which was about 30 seconds:
This was my initial test. No heat load still, but going from idle down to -100C. This reflects how temperature responds at the probe, with LN2 applied to the pot. In about 6 minutes and 40 seconds, the probe went from 15C to -100C with consistent pouring to keep it near full:
My next test had a data gathering error - the Tenma 72-7712 software program which creates an excel spreadsheet and a graph, sometimes crashes. It crashed, and no data was gathered. This test was with a heat load applied, bringing the pot from 15C down to full pot, wherever that ended up on the temp gauge. This was abandoned before full pot was reached, due to the software error.
My next test was pulling the pot temperature down to -115C, then beginning to collect data, until full pot was reached:
After full pot was reached, I recalibrated the probe to -195.5C when maintaining full pot with no heat load - this doesn't matter, except all of these tests will be performed again, because I recalibrated the probe again after testing (based on dipping the probe directly into LN2, and setting the probe to read just below -195.5C). The beginning of this graph reflects a full pot with no heat load and temps consistently at ~-195C. When temps begin to rise, that reflects powering the heat load on, with consistent pouring to maintain full pot without overflow. When the graph levels out again, that reflects equilibrium - heat load fully powered, pot maintained at full without overflow. It held the probe to -178C in this state. Then I stopped maintaining the pot - when temps began to rise reflects when all LN2 was boiled off and was no longer audible. Even with barely any LN2 left in the pot, the temp probe remained stable at that -178C equilibrium point until the LN2 was gone.
This test reflects attempting to maintain a temperature of -115C with a heat load applied, with beginning recording when the probe hit -120C from a small splash of LN2 just prior to recording. From 0 minutes to 1.5 minutes, the temp was swinging high and low as I got control of the pot. From minute 2 to minute 6, approximately 4 minutes, I maintained temps to the best of my ability - constant maintenance with absolute concentration - results were no warmer than -113c or colder than -119C during this period. Realistically, to control temps to this degree I would have needed someone else to run the bench while I maintained the pot, and the heat load would have needed to remain constant as it was throughout this entire test. After the 6 minute mark of the test, I slammed the pot to see how it would respond. This test also represents a fully frosted pot under real benching conditions (the pot has been cold, may have warmed up a bit, then frosted again - this tends to affect how the pot responds to LN2):
