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Acceptable difference in temp and RH ranges between dataloggers


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    • #137009
      Bill Robinson

      Just joined the forum, and thanks for having me. I’m testing 3 older Hobo U12 dataloggers against a new U12 datalogger to see how temp and RH differ between the old dataloggers and the new. I’m wondering at what range of difference I would have to get the older dataloggers professionally calibrated. The goal is to get a year’s data from all four loggers. I put all four dataloggers in an archival print box for two days, measuring temp and RH at 15 minute intervals. The average differences in readings are as follows:

      New logger vs. old logger #1:
      Temp .467938 higher in new logger
      RH 1.00795 higher in old logger

      New logger vs. old logger #2:
      Temp .275845 higher in new logger
      RH .788077 higher in old logger

      New logger vs. old logger #3:
      Temp .405985 higher in new logger
      RH .242103 higher in old logger

      Thanks for any help!

    • #137028
      Annabelle Fichtner

      Good morning, Bill. Excellent question, and your testing method sounds great! I would like to pass along some info from AIC Fellow M. Susan Berger. While the difference the old and new dataloggers is not significant enough to cause serious concern, you could double check them both using a sling psychrometer which is considered the standard for accurate measurement and see which is more accurate. However, the differences you are seeing are not huge cause for concern, and would certainly not alter the appearance of any graphs of comparable data (if your intention is to graph and analyze the year’s worth).

      If you are interested in calibration though, it may be worth calling ONSET and getting their input as well. Here is the number for their technical support: 1-800-564-4377


    • #137029
      Douglas Sanders

      Bill- Your stated variance between the old loggers and new falls well within the accuracy one can expect from these dataloggers. Hobo reports an accuracy for the U12 of “Temperature: ± 0.35°C from 0° to 50°C (± 0.63°F from 32° to 122°F) RH: ± 2.5% from 10% to 90% RH typical”. If you were to send them off for calibration, I don’t think you could reasonably expect any less deviation.


    • #137030
      Bill Robinson

      Sounds good. Thanks Annabelle and Doug!

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