A faulty sheathed max. thermometer

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Nick Robinson
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Joined: Mon Dec 14, 2015 6:04 pm

A faulty sheathed max. thermometer

Post by Nick Robinson » Sat Jul 23, 2016 1:11 pm

I've had a bad run with my sheathed maximum thermometers - three in twelve months.
The first I broke while adjusting after the 0900 obs., and the second had an irremovable break in the mercury column, and now the third has a fault.
When releasing the mercury column passed the constriction, I have to continually shake the thermometer, instead of the normal single shake. This in turn sometimes splits the mercury column. Yesterday I spoke to the guy at Metcheck ( Skyview Systems of Sudbury), and he was of the opinion that this is a common problem with new sheathed maximum thermometers, due to the the mercury substitute now being used. I was under the impression that after the new European regulations, mercury was still permitted in scientific instruments, including maximum thermometers.
Any comments on this would be much appreciated.
Nick Robinson,
Colchester NE2

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Nicholas Gardner
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Location: Rural riverside valley location near the village of Newton Poppleford and 2 km from the sea.
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Re: A faulty sheathed max. thermometer

Post by Nicholas Gardner » Sun Jul 24, 2016 7:11 pm

Nick, my old 'faithful' maximum sheathed thermometer that I have had for over 20 years developed a gap in the mercury column after I had dropped (fell onto grass so didn't break) meaning that it continually over-read by about 0.6°C. No matter what I did I couldn't get rid of that gap.

Then I thought that if I put it in the freezer the mercury would shrink enough so the 'gap' would end up being pulled into the main mercury reservoir and thus, disappear. This didn't happen in my case as the freezer wasn't cold enough as the gap was too far up the mercury column, but in your case this may work?

I cured the problem by burying the thermometer in dry ice (solid carbon dioxide - I used to work in a laboratory that used the stuff) and that solved the 'gap' issue.
Otter Valley Weather
Near Newton Poppleford, Sidmouth - Devon
50:41N 3:17 W; 20 metres AMSL; Station Grade B-BAAA37
http://www.ottervalleyweather.me.uk

Nick Robinson
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Joined: Mon Dec 14, 2015 6:04 pm

Re: A faulty sheathed max. thermometer

Post by Nick Robinson » Mon Jul 25, 2016 6:04 am

Nicholas,

Thank goodness I'm not the only one with Max.thermometer problems.
During my years at sea serving on a Voluntary Reporting Ship, I only used the one max.thermometer, (replacements were readily available) - and that was with the rocking and rolling and banging of the ship in bad weather .

Just about to order a new one.

Nick Robinson

Nick Robinson
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Joined: Mon Dec 14, 2015 6:04 pm

Re: A faulty sheathed max. thermometer

Post by Nick Robinson » Mon Jul 25, 2016 11:54 am

This morning I telephoned Skyview to order a replacement sheathed max. thermometer and they told me that they were out of stock, and held little hope of obtaining a fresh supply. Perhaps this type of thermometers are becoming obsolete - I do hope not.

Nick Robinson,

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Michael Brown
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Re: A faulty sheathed max. thermometer

Post by Michael Brown » Sun Aug 07, 2016 12:06 pm

I have a mercury, sheathed max thermometer which has always read 0.6˚C higher than it should when compared to the 'normal' thermometer of the same pattern. there are no breaks or other problems with the column, it is just a bad reading. When compared to my electronic unit it gives the same problem too.
It worries me slighty because where it must have been in the past, has clearly recorded all their values with a 0.6˚C error on them, I am sure that they were not aware of this. How many other might be in the same position?

Mike

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