Pagina 4 di 6 PrimaPrima ... 23456 UltimaUltima
Risultati da 31 a 40 di 52
  1. #31
    Iridescenza
    Data Registrazione
    Oct 2016
    Località
    Zurigo
    Messaggi
    21
    Dear Bruno

    This is also my understanding: thermal cameras detect infrared radiation emitted by objects which permit conclusions on the surface (and not the air!) temperature.

    I can imagine that thermal cameras can help to answer different questions related to frost hollows, but I'm aware that this technology has it's difficulties and drawbacks:

    - Which is the coldest point in a frost hollow? This question seems to be trivial in cone-shaped frost hollows: here it is the lowest point. But what if a depression has a more complex topography? This example of a depression near Brünigpass in Central Switzerland is, if you look at the map, not so clear. It is roughly divided into two parts: the southeastern part is a little bit deeper, but is surrounded by steeper slopes. If you zoom in, you recognize the small hill called 'Benedichtenwald' with a forest on it. East of this little hill there is a secondary depression which is not as deep as the main depression but it has a more open character. You can of course distribute several loggers over the area but with a thermal cam I would expect to receive an approximation of the spatial distribution of the temperature. Here is another nice example from the Jura with a complex topography.

    - Where on a slope is the cold air produced? Where are the preferential flowpaths of the cold air? For the first question I assume that a thermal camera with sufficient reach can provide insight which is very difficult to gain with point measurements. For the second question a thermal camera can give hints where the most appropriate location for a smoke experiment is.

    Regards, Stephan

    P.S. Thanks again for the hint to the book from David Whiteman - a must-read!

  2. #32
    Presidente, Tesoriere M3V
    Resp. Progetto Doline

    Rete Stazioni M3V
    L'avatar di Rizzo69
    Data Registrazione
    Jun 2008
    Località
    Levico Terme (TN) 490 m.
    Messaggi
    1,372
    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    Dear Giampaolo

    Don't worry about your English, I think I understand you perfectly and my English is far from being perfect!

    Your observation in the frost hollow of Avalina Regnalt is also covered by litterature: a good sky view factor is by far more important than the depth of a frost hollow (e.g. http://journals.ametsoc.org/doi/pdf/...A%3E2.0.CO%3B2).

    Regarding the instruments I use: Bruno's report "Le fabbriche naturali del freddo" was very inspiring for me. For quite a while I was thinking about working with HOBO Onset dataloggers, which have a very good reputation. A colleague of mine who is also working in frost hollows suggested me to try Tinytag dataloggers from Gemini because he made very good experiences with this loggers.

    Now I have two types of loggers in use:

    http://www.geminidataloggers.de/data...lus-2/tgp-4104 together with http://www.geminidataloggers.de/prob...es/pb-6005-1m5 at the bottom of my two frost hollows. They have a measurement range down to -50 °C.

    For tests campaigns and at the upper part of my frost hollows I a using http://www.geminidataloggers.de/data...talk-2/tk-4023. They are small and a little bit cheaper, measurement range goes down to -40 °C. The also fit in passive radiation shields like Davis 7714 or http://www.geminidataloggers.de/acce...other/acs-5050.

    Wind would also be perfect... If my financial possibilities would allow it then this type of weather station would be an option: http://www.lufft.com/de/produkte/all...sorik-8370u01/

    It is good news to hear the you have so few problems with vandalism or theft. Do you have an idea why it happened twice at the same place? Did you took protection measures?

    Best regards, Stephan
    Dear Stephan, I thank you for the link to the publication, I had the opportunity to read some of Whiteman works thanks to Bruno.
    As regards the sensors, I used for some years the Hobo, have a defect that they are very expensive and do not drop below -40 ° C, however, had the convenience of having the hygrometer and to have a “shuttle” to download the data, so you don’t have to use a computer whose batteries run down quickly or to use multiple sensors. The shuttle is convenient because you can download in its memory the data from different sensors.

    I don’t know the Gemini, I’ve read that the TGP 4104 have good accuracy at temperatures between -50 ° C and + 30 ° C (0.4 ° C), however, I’ve read that while measuring up to -50 ° C have an operational range of -40 ° C which is a bit 'strange.

    I saw that the ones you used you are slightly less accurate at temperatures below -20 ° C, but they look solid products.

    Beautiful Lufft station with sonic anemometer, do you know how much it costs?

    As for the theft, are all successes both times in the summer, when they pass many walkers who go to search for mushrooms and there are cows with the shepherds, I avoided to install in the summer at this site.

    Best regards.

    Giampaolo
    File Allegati File Allegati
    Freddofili si nasce "dolinatori" si diventa


    stazione online con Weather Display Live
    http://www.meteolevicoterme.it/Dati-...ne-Online.aspx

  3. #33
    Iridescenza
    Data Registrazione
    Oct 2016
    Località
    Zurigo
    Messaggi
    21
    Citazione Originariamente Scritto da Rizzo69 Visualizza Messaggio
    Dear Stephan, I thank you for the link to the publication, I had the opportunity to read some of Whiteman works thanks to Bruno.
    As regards the sensors, I used for some years the Hobo, have a defect that they are very expensive and do not drop below -40 ° C, however, had the convenience of having the hygrometer and to have a “shuttle” to download the data, so you don’t have to use a computer whose batteries run down quickly or to use multiple sensors. The shuttle is convenient because you can download in its memory the data from different sensors.

    I don’t know the Gemini, I’ve read that the TGP 4104 have good accuracy at temperatures between -50 ° C and + 30 ° C (0.4 ° C), however, I’ve read that while measuring up to -50 ° C have an operational range of -40 ° C which is a bit 'strange.

    I saw that the ones you used you are slightly less accurate at temperatures below -20 ° C, but they look solid products.

    Beautiful Lufft station with sonic anemometer, do you know how much it costs?

    As for the theft, are all successes both times in the summer, when they pass many walkers who go to search for mushrooms and there are cows with the shepherds, I avoided to install in the summer at this site.

    Best regards.

    Giampaolo
    Dear Giampaolo

    HOBO dataloggers definitively have a good reputation. The shuttle is a clever way to download efficiently data - can you use it also at very low temperatures? On January 6 (this was day 1 of the arctic cold spell) I visited Hintergräppelen in order to experience really cold temperatures live. I also tried to download my data with a notebook but it freezed at - 34°C. As a consequence I bought a used Panasonic Toughbook which is designed for use under rugged conditions and has an extra long battery runtime. The drawback: it is quite heavy...

    So far I'm happy with my Gemini Dataloggers. They are easy to use and quite robust. I am aware of the gap between the reading range (down to - 50°C and the operational range (down to - 40°C). The loggers that I use are originally desigend for industrial and process applications. In this setting it is possible in almost every case that you install the logger under conditions with >- 40°C and only the sensor will be placed in conditions with <- 40°C. As far as I learned from the vendors (I asked Onset and Gemini) the performance of the battery is the limiting factor. There is a good chance that the logger will work outside of the specified range but there is no guarantee. In order to ensure good operation it would be the best to place the logger on or even in the ground. As soon as snow falls, the snow cover will insulate the logger. I could not realize this setup at Sämtisersee and Hintergräppelen (the stations are flood-prone and at risk by grazing cattle) but it is definitively an option for other stations.

    I learned from Bruno that you are using CryoTemp loggers (http://www.madgetech.com/pdf_files/d...ryoTemp_DS.pdf) for your most extreme frost hollows. Are you satisfied with this logger? Did you evaluated other options?

    I found prices for the Lufft station on the following sites:
    - https://www.meteo.cc/Multifunktionssensor-WS600-UMB --> CHF 3229 (= EUR 3030 --> as always, Switzerland is very expensive...)
    - http://lufft-messtechnik.de/index.ht...undsysteme.htm --> EUR 2415

    Best regards, Stephan

  4. #34
    Socio Onorario M3V
    Data Registrazione
    Sep 2007
    Località
    Ponte nelle Alpi (BL)
    Messaggi
    2,603
    Dear Stephan, I try to answer you regarding the data logger we're using...


    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    HOBO dataloggers definitively have a good reputation. The shuttle is a clever way to download efficiently data - can you use it also at very low temperatures?
    Yes, the shuttle works also at very low temperatures. It takes only 20-30 seconds for data download (1-4 months of data) so the electronic has underwent to extreme cold for a while.
    Hobo dataloggers have the Achille's heel in the batteries when temperature drop down below -40°C. (they lose a lot of their charge)

  5. #35
    Socio Onorario M3V
    Data Registrazione
    Sep 2007
    Località
    Ponte nelle Alpi (BL)
    Messaggi
    2,603
    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    I learned from Bruno that you are using CryoTemp loggers (http://www.madgetech.com/pdf_files/d...ryoTemp_DS.pdf) for your most extreme frost hollows. Are you satisfied with this logger? Did you evaluated other options?
    The Cryotemps can work down to -86°C (thaks to the special battery) so we aren't worry at the coldest hollows (above 2000-2500 m). Furthermore our Cryotemps lasted 3-5 years before replacing batteries.
    Sore points: there isn't any battery level control and above all there isn't any warning regarding "low battery". This is very strange and really problematic.
    Moreover the logger is sealed so you would have to send it to the company (USA) to replace the battery.

  6. #36
    Presidente, Tesoriere M3V
    Resp. Progetto Doline

    Rete Stazioni M3V
    L'avatar di Rizzo69
    Data Registrazione
    Jun 2008
    Località
    Levico Terme (TN) 490 m.
    Messaggi
    1,372
    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    Dear Giampaolo

    HOBO dataloggers definitively have a good reputation. The shuttle is a clever way to download efficiently data - can you use it also at very low temperatures? On January 6 (this was day 1 of the arctic cold spell) I visited Hintergräppelen in order to experience really cold temperatures live. I also tried to download my data with a notebook but it freezed at - 34°C. As a consequence I bought a used Panasonic Toughbook which is designed for use under rugged conditions and has an extra long battery runtime. The drawback: it is quite heavy...

    So far I'm happy with my Gemini Dataloggers. They are easy to use and quite robust. I am aware of the gap between the reading range (down to - 50°C and the operational range (down to - 40°C). The loggers that I use are originally desigend for industrial and process applications. In this setting it is possible in almost every case that you install the logger under conditions with >- 40°C and only the sensor will be placed in conditions with <- 40°C. As far as I learned from the vendors (I asked Onset and Gemini) the performance of the battery is the limiting factor. There is a good chance that the logger will work outside of the specified range but there is no guarantee. In order to ensure good operation it would be the best to place the logger on or even in the ground. As soon as snow falls, the snow cover will insulate the logger. I could not realize this setup at Sämtisersee and Hintergräppelen (the stations are flood-prone and at risk by grazing cattle) but it is definitively an option for other stations.

    I learned from Bruno that you are using CryoTemp loggers (http://www.madgetech.com/pdf_files/d...ryoTemp_DS.pdf) for your most extreme frost hollows. Are you satisfied with this logger? Did you evaluated other options?

    I found prices for the Lufft station on the following sites:
    - https://www.meteo.cc/Multifunktionssensor-WS600-UMB --> CHF 3229 (= EUR 3030 --> as always, Switzerland is very expensive...)
    - http://lufft-messtechnik.de/index.ht...undsysteme.htm --> EUR 2415

    Best regards, Stephan
    Dear Stephan, I agree with what Bruno wrote about the Hobo and Cryotemp. The Cryotemp are fantastic but very expensive (about 300 Euro) and there are problems with the battery.
    I used different sensors in the past:
    The OmegaOM63, but had serious problem with moisture coming into the sensor is not sealed and lost data.
    Then I used the Mininomad of Omega, it is cheap but it need a reader (250 Euro) and end the battery dure less than two years and you can not replace like the Cryotemp.
    In the past we used and still are using the i-button of the maxim, that cost little, they are waterproof and last for six years
    This year I bought fifteen RC4 of Elitech, they have the advantage of costing very cheap. I put the sensor with the display in a bag and leave the probe outside, the software of the RC4 is very easy, you can export the data in Word, Excel, TXT, PDF.

    http://www.elitech.uk.com/news/Elite...logger_67.html


    Best Regards.
    Thank you for the informations about the prices of the weather stations
    Giampaolo
    Freddofili si nasce "dolinatori" si diventa


    stazione online con Weather Display Live
    http://www.meteolevicoterme.it/Dati-...ne-Online.aspx

  7. #37
    Iridescenza
    Data Registrazione
    Oct 2016
    Località
    Zurigo
    Messaggi
    21
    Dear Bruno, dear Giampaolo

    Sorry for my late response, I was absent for holiday. The Cryotemp sounds interesting but I see the drawbacks... I didn't found any information about the response time of the (internal?) probe of the Cryotemp. Can you say someting about it? How much do you pay for a new battery (shipping costs + battery + labour costs)?

    Edit: It just surfed the Madgetech Homepage and found out that the have another interesting product: http://international.madgetech.com/d...s/lyotemp.html --> The LyoTemp Data Logger has a range to "only" -60°C but an external probe and a calibrated accuracy of 0.5 °C (vs. 1 °C for the CryoTemp). Do you have tested this product?

    Best regards, Stephan
    Ultima modifica di Stephan; 27-02-2017 alle 20:51 Motivo: addendum for LyoTemp

  8. #38
    Presidente, Tesoriere M3V
    Resp. Progetto Doline

    Rete Stazioni M3V
    L'avatar di Rizzo69
    Data Registrazione
    Jun 2008
    Località
    Levico Terme (TN) 490 m.
    Messaggi
    1,372
    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    Dear Bruno, dear Giampaolo

    Sorry for my late response, I was absent for holiday. The Cryotemp sounds interesting but I see the drawbacks... I didn't found any information about the response time of the (internal?) probe of the Cryotemp. Can you say someting about it? How much do you pay for a new battery (shipping costs + battery + labour costs)?

    Edit: It just surfed the Madgetech Homepage and found out that the have another interesting product: http://international.madgetech.com/d...s/lyotemp.html --> The LyoTemp Data Logger has a range to "only" -60°C but an external probe and a calibrated accuracy of 0.5 °C (vs. 1 °C for the CryoTemp). Do you have tested this product?

    Best regards, Stephan
    Dear Stephan, also excuse me for my late response.
    Maybe Bruno knows answer with regard to the replacement costs of the Cryotemp batteries , and for the response time of the probe, I've never done.
    Thanks for the report of the new product, I do not know it,
    Best regards.
    Giampaolo
    Freddofili si nasce "dolinatori" si diventa


    stazione online con Weather Display Live
    http://www.meteolevicoterme.it/Dati-...ne-Online.aspx

  9. #39
    Socio Onorario M3V
    Data Registrazione
    Sep 2007
    Località
    Ponte nelle Alpi (BL)
    Messaggi
    2,603
    Citazione Originariamente Scritto da Stephan Visualizza Messaggio
    Dear Bruno, dear Giampaolo

    Sorry for my late response, I was absent for holiday. The Cryotemp sounds interesting but I see the drawbacks... I didn't found any information about the response time of the (internal?) probe of the Cryotemp. Can you say someting about it? How much do you pay for a new battery (shipping costs + battery + labour costs)?

    Edit: It just surfed the Madgetech Homepage and found out that the have another interesting product: http://international.madgetech.com/d...s/lyotemp.html --> The LyoTemp Data Logger has a range to "only" -60°C but an external probe and a calibrated accuracy of 0.5 °C (vs. 1 °C for the CryoTemp). Do you have tested this product?

    Best regards, Stephan
    Dear Stephan, I do apologize, indeed…I haven’t noticed your message, I read it only this morning.

    Regarding the response time (or constant time) of Cryotemp I can’t give you any informations. It is surely very similar or identical to Hobo’s one. I compare them many times and the variations were almost the same. About this topic I (modern sensors and dataloggers with very short response time) we have to pay close attention, because these dataloggers could be "too fast" in measuring, so you can’t compare historical data recorded with classic mercury or alcohol thermometers, that had a longer response time (5-10 minutes?).
    But this is only a thought of mine.

    With regards to changing battery of Cryotemp I don’t know how much it costs (I have opened myself the datalogger and changed the battery, purchased in my town). Anyway, if you want to ship to do it, I think you’ll have to pay beteew 50 and-100 euros.
    Finally, I had just seen the LyoTemp, it seems a good product, considering di external probe and especially the higher accuracy, but I can’t tell you anything about it.

    Warmest regards and again sorry for the late response
    Bruno

  10. #40
    Iridescenza
    Data Registrazione
    Oct 2016
    Località
    Zurigo
    Messaggi
    21
    Dear all

    I took advantage of the actual cold spell and made a short trip to the frost hollow at Hintergräppelen this morning. It was definitely worth the effort, I could enjoy some -21.4 °C (measured with the handheld thermometer). The following film sholud give an impressing of the descent into the frost hollow:



    My station registered a minimum of -21.8 °C this morning and even -27.2 °C on Thursday morning:



    Here an additional foto from the bottom of the frost hollow towards the rising sun:



    Interesting detail: in the foreground on the left side you recognize a crack in the snowcover. There were quite a lot of them all over the frost hollow. The day before the maximum temperature stayed just below 0 °C but the sun radiation was very intense. This resulted in thawing and refreezing of the surface of the snowcover. I interpretate these cracks as stress cracks in the contracting snow cover due to the falling temperature.

    Best regards, Stephan

Permessi di Scrittura

  • Tu non puoi inviare nuove discussioni
  • Tu non puoi inviare risposte
  • Tu non puoi inviare allegati
  • Tu non puoi modificare i tuoi messaggi
  •