Author Topic: Change in outer cylinder mass?  (Read 1420 times)

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Offline miraculon

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Change in outer cylinder mass?
« on: February 11, 2022, 09:54:21 AM »
One of my outer cylinders that I use for CoCoRaHS has apparently changed mass over time. The original label said 459g, I re-weighed it and it shows 456g on both the Escali scale and a postal scale that I have. I am certain that my original mass measurement was correct.

I use a 500g test weight that shows 501g in the garage scale (w/heater) and the basement Escali shows it as 500g (tipping to 501g sometimes) each time I measure the snow mass.

Can the loss of plasticizers (VOC?) cause this? Has anyone else seen an apparent mass change for an empty cylinder?

Greg H.


Blitzortung Stations #706 and #1682
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Offline PaulMy

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Re: Change in outer cylinder mass?
« Reply #1 on: February 11, 2022, 01:46:50 PM »
Hi Greg,
My scale isn't a high precision scale but it does measure in 0.5 gm increment.  I have 5 outer tubes, 2 for daily precipitation catchment and 2 for replacement at 8:00 am, and the other for measuring new snow and total snow on the ground SWE.  A couple are 8 years old and the most recent this fall from CoCoRaHS Canada.  I got the scale before first snowfall in November and empty weighing for the 5 tubes at the time varied from 451.0 to 460.5 gm.  I have continued to weigh the empty tubes after each rain and snowfall and have found that the same empty outer tube can weigh different on different days, with a +/- difference of up to 3 gm.  I've only submitted the weight method SWE to CoCoRaHS for my weekly total snow on the ground where any difference is relative minor.  I wait for the snow melting to submit the daily SWE.

A bigger beef is that I submit in metric and CoCoRaHS converts to Imperial in their records and then display back in metric and with the rounding then does not display nor log what I submitted - i.e.  0.6 mm becomes 0.5 mm and 26.0 mm becomes 25.9 mm, and in metric the increments are in .2s so 0.5 and 25.9 shouldn't exist. 


Enjoy,
Paul
Davis Vantage Pro 2 Plus 24-FARS Wireless - Komoka, ON Canada
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Blitzortung Station #1076


Offline miraculon

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Re: Change in outer cylinder mass?
« Reply #2 on: February 11, 2022, 02:54:02 PM »
Hmmm.. Interesting. My recent measurements of the suspect cylinder have been consistent from day-to-day. I also weigh the 500g calibration weight each time and the scales are repeatable.

It might be interesting to see if your variation is due to drift in the scale or some other factor when using a calibration weight. I picked 500g since it falls in range with a reasonable rain amount.

Thanks for the response, Paul.

Greg H.




Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline PaulMy

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Re: Change in outer cylinder mass?
« Reply #3 on: February 11, 2022, 04:00:40 PM »
Hi Greg,
One thing I've noticed is that when I bring in the full cylinder and weigh it, then leave it for a while while snow is melting (I cover it to hopefully avoid evaporation) and then when snow is melted I weigh the full cylinder again and often see a 0.5 gm difference (mostly less).  I've wondered if the temperature difference between just coming from outside and then leaving it inside for a while could affect the weight?!?.  After the snow is melted I pour it in an inner tube to get the actual mm, and then I weigh the empty cylinder after the melt is complete. 

Maybe it is my scale as it is a cheapy from CTC.  I'll experiment by also weighing the cylinders before I put them outside and compare that to the empty cylinder when I bring it in the next morning.  I'll also do the same for the cylinder I use to measure the new snow and the snow on the ground on Mondays as then I get two empty measurements of the same cylinder within a short period.  I'll also check with another kitchen scale...

Enjoy,
Paul

Davis Vantage Pro 2 Plus 24-FARS Wireless - Komoka, ON Canada
Envoy/USB Logger/Cumulus v1.9.4  www.komokaweather.com  
WFL/CMX www.komokaweather.com/komokaweather-ca2/index.php
WLL/CMX www.komokaweather.com/cumulusmxwll/index.htm
WLL/CMX www.komokaweather.com/cumulusmxwll/index.html
WLL/CMX www.komokaweather.com/cumulusmxwll/index.php
Blitzortung Station #1076


 

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