11 replies to this topic

[A Scottish Winter's Tale]

I'm looking to get a maximum and minimum thermometers for the winter and I'd like to know:

- Which one is the best
- The cheapest
- Does it require a Stevenson Screen
- How to use and set it
- Any other details

[Terminal Moraine]

A Winter, on 25 September 2011 - 13:24 , said:

I'm looking to get a maximum and minimum thermometers for the winter and I'd like to know:

- Which one is the best
- The cheapest
- Does it require a Stevenson Screen
- How to use and set it
- Any other details

What you buy depends to a large extent to what you want from the thermometer(s). If you want just a rough guide to the temperature you can buy a Six's thermometer, which is a U bulb mounted on a plastic frame and scale, from any garden centre for a few quid. You'd need to site it about 4 feet above the ground out of direct sunlight but it wouldn't be worth going to the expense of buying a Stevenson's Screen as the thermometer is only accurate to about 2c and even this tends to drift over a relatively short period of time.
If you're looking for accuracy then separate max' and min' thermometers mounted in a screen are the way to go. The downside is they're expensive, around £80 each including postage, and a Stevenson Screen will cost another £300 minimum.
The U bulb thermometers are set using a magnet which draws the indice back to the mercury column. The separate thermometes are set differently, by tipping the minimum bulb end up so that the indice slides back to the column of spirit, the maximum is set be shaking it to force the column of mercury back past a constriction in the tube which holds the mercury in place once the maximum temperature has been reached.

[A Scottish Winter's Tale]

Terminal Moraine, on 25 September 2011 - 14:37 , said:

If you want just a rough guide to the temperature you can buy a Six's thermometer, which is a U bulb mounted on a plastic frame and scale, from any garden centre for a few quid.

So this records both max and min temps and can you leave it overnight to record min temps and be able to see the recorded temperature in the morning?

[Terminal Moraine]

A Winter, on 25 September 2011 - 17:31 , said:

So this records both max and min temps and can you leave it overnight to record min temps and be able to see the recorded temperature in the morning?

Yes, that's right. You can pick one up for about £6 or so at a garden centre.
The thermometer has a bit of metal ( indice ) above the column of mercury at either side. When the temperature rises it pushes the indice up the tube and leaves it behind when it falls, you read the bottom of the indice against the temperature scale to give the maximum temperature.
The reverse is true as the temperature falls, the mercury column rises up the opposite side of the scale, pushing the indice with it, when the temperature rises it leaves it behind and you read the bottom of the indice against the scale for the minimum temperature.

[johnholmes]

http://www.weathershop.co.uk/
the link above is well worth looking at for lots of information to supplement the first class advice TM has given you.
Perhaps you would be tempted to spend £20-30 for a remote wireless sensor that does all that for you from the comfort of your house. Or maybe you prefer to do as the more keen amateurs do and go out each morning and evening and manually reset your max/min thermometer as TM has explained.
Perhaps your parents might talk to Santa and you could get both!
Welcome to the weather world, its fun, and extemely addictive!

[Snow? norfolk n chance]

mine is a wireless sensor, called lexibook meteoClock, from argos. think it was around £37, but very tricky to find a shaded spot from may-jul

too much sun radiation gives temp readings too high, too sheltered and close to ground readings too low, and main indoor unit has to be close to outdoor sensor or signal goes

[Terminal Moraine]

snow? norfolk n chance, on 25 September 2011 - 19:17 , said:

mine is a wireless sensor, called lexibook meteoClock, from argos. think it was around £37, but very tricky to find a shaded spot from may-jul

too much sun radiation gives temp readings too high, too sheltered and close to ground readings too low, and main indoor unit has to be close to outdoor sensor or signal goes

Depending on you sensor ( the shape and dimensions of it that is ) it's possible to buy a mini-screen to shield it from direct sunshine and background radiation, I think they're about £50.
What's the maximum distance the sensor can be from the indoor unit before the signal fails? If it's a reasonable distance you could mount the sensor and screen on a post somewhere near the house, it would certainly overcome the problem of direct sunshine.

[Corrigan87]

I use a wireless sensor mounted underneath a gutter north facing so it never gets sunlight whatever the month or time.

On a different note, when I was studying Ecology with the Open University, we had to do an experiment putting thermometers underneath an oak tree and another exposed to the elements. It started in October and the idea was that the difference between the two got smaller as the tree lost its leaves. When the group collated the results someone obviouslt hadnt covered the exposed one in leaves so they reported a temp of about 47 degrees because the direct sunlight in November was that strong! Shows what a difference direct sunlight can give.

[A Scottish Winter's Tale]

I've got my thermometer.

One thing I find strange that the indice that's meant to record the maximum temperature sometimes doesn't reach the proper highest temperature i.e the current temperature is 20C but the highest recorded temp is 15C.

One other question is what time do you record and restet your thermometer readings.

Like if you decided to record minumum temperatures starting from re-setting it at 9PM and checking/re-setting at 9AM - you may not know whether the minumum temperature happened on 16th or the 17th or the minimum temperature could have happened during the daytime. How do you work it out?

[Terminal Moraine]

A Winter, on 03 October 2011 - 23:11 , said:

I've got my thermometer.

One thing I find strange that the indice that's meant to record the maximum temperature sometimes doesn't reach the proper highest temperature i.e the current temperature is 20C but the highest recorded temp is 15C.

One other question is what time do you record and restet your thermometer readings.

Like if you decided to record minumum temperatures starting from re-setting it at 9PM and checking/re-setting at 9AM - you may not know whether the minumum temperature happened on 16th or the 17th or the minimum temperature could have happened during the daytime. How do you work it out?

Not quite sure what's happening regarding the indice. Assuming you're reading the correct side for the maximum?
If the temperatue is 20c the indice will either be right on the mercury column which means the temperature is still rising, or it will be above it and the bottom end of the indice will indicate the maximum temperature.
Withe regard to the timing of setting your thermometer, there's no simple answer.
The standard meteorological day for temperature and rainfall runs from 0900-0900 g.m.t, this means that the thermometers are read and set at that time and the maximum temperature is allocated to the day before and the minimum to the day you're doing the reading. The downside of that is that on a very cold morning, say with a temp' of -8c, you'll take the reading of -8c and that will be the minimum. You'll then set the thermometer and even if the temperature rises during the day and remains above freezing for the whole of the next night the minimum the following morning at 0900 will be -8c. The opposite can also apply to the maximum. You could have a very cold morning and a very cold day with the maximum below 0c all day, but then the temperature rises after midnight and the reading at 0900 the next morning is, say, 6c , this will then be the maximum for the previous day.
Really the only way of knowing whether a max' or a min' occurred on which day is to re-set the themometers at midnight which is not very practial, or to invest in some sort of automatic weather station which gives the times of the highest and lowest readings.

[A Scottish Winter's Tale]

I think I'll:

Reset and record temps at 9AM and then Reset/Record again at 6PM or so. I'll get the maximum temperatures of let's say December 6th and Minimums of Night 5th/6th and 6th/7th.

[wimblettben]

Well my temperature reading times that I have for my records are usually 7:00AM for the mourning and 10:00PM for the evening.