infrared thermometer

Maplin usually have some that are fairly inexpensive.

maplin 30 quid

I got one from CPC for about £30.

In message , mrcheerful . wrote

If pointing at a clear sky you are looking through the atmosphere into space. Space will be around absolute zero (-273 degrees C) - attenuated by the atmosphere and limited to the range of the device. You may not see the temperatures you expect to see :)

If looking at low clouds the water vapour could be acting like a mirror and reflecting the ground temperature.

Cheaper instruments @ £12 (with a smaller temperature range) can be obtained on Ebay.

Note that the Ebay item required a 12V battery - not supplied.

My CPC device takes 2 off AAA size 1.5V batteries

Be aware that these instruments are measuring an area of diameter 3 or

Actually, it's about 3K (-270C) due to heat left from the big bang in the form of the cosmic microwave background. However, you won't get a digital thermometer to register that.

No, I get believable readings from clouds, typically -40 to -50, which agrees with what aircraft report as the outside temperature.

If the OP isn't in a hurry for one, these things do turn up on special offer from time to time.

Fluke do a nice one...Model 62...but it ain't cheap! Cost around £60

I bought one of those about 12 months ago and it is perfect for winding up the landlord of my local real ale pub. The one thing he hates is to be told that is serving his beer at the wrong temperature. A quick pull of the trigger and he is convinced.

On the other hand, I did find it very difficult to balance my heating with it. I ended up measuring the temp of the rad at point of entry and exit. Trying to measure the pipes proved very variable.

Dave

They don't work on bare copper (looks like a mirror to IR).

In message , Andrew Gabriel wrote

See

Check the section on emissivity. Note also the warning about the field of view of the sensor - for a 15 mm pipe to fill the field of view you may have to be as close as 4 inches.

|Andy Hall wrote: | |> On 2006-10-15 11:48:31 +0100, "Ron" said: |> |>> Hi, I am becoming obsessed :-) with temperature and heat loss etc. |>> around my house and thought I would get an infrared thermometer to |>> measure wall temperatures and other things such as the temerature of |>> overhead clouds if possible. Any suggestions as to what type of |>> infrared thermometer I should get? Not too expensive as my grandson is |>> buying it for my birthday. |>> Thanks Ron |> |> |> |> Maplin usually have some that are fairly inexpensive. | |I bought one of those about 12 months ago and it is perfect for winding |up the landlord of my local real ale pub. The one thing he hates is to |be told that is serving his beer at the wrong temperature. A quick pull |of the trigger and he is convinced.

Surely it measured the temperature of the outside of the glass not the temperature of the beer ;-)

Clouds at -40 to -50? - I don't think so. You have to go to around

CRB

The error with low cloud is probably because their emissivity is less than the fixed value of about 0.85-0.9 which is programmed into simple IR thermometers. The instrument detects a certain quantity of IR radiation, but reports it as coming from a cooler object than is actually the case.

IR thermometers with an adjustable setting for the assumed emissivity are much more expensive.

LOL Yes. But since the glass is only a container that is quite thin, the contents will be equal to the outside of the glass.

Just wait a minute, I have a hook in my mouth and I must get rid of it :-)

Dave

That depends where you point the thermometer. You could point it at the top of the beer rather than the glass, surely.

|Dave Fawthrop wrote: | |> On Mon, 16 Oct 2006 23:04:12 +0100, Dave wrote: |> |> |Andy Hall wrote: |> | |> |> On 2006-10-15 11:48:31 +0100, "Ron" said: |> |> |> |>> Hi, I am becoming obsessed :-) with temperature and heat loss etc. |> |>> around my house and thought I would get an infrared thermometer to |> |>> measure wall temperatures and other things such as the temerature of |> |>> overhead clouds if possible. Any suggestions as to what type of |> |>> infrared thermometer I should get? Not too expensive as my grandson is |> |>> buying it for my birthday. |> |>> Thanks Ron |> |> |> |> |> |> |> |> Maplin usually have some that are fairly inexpensive. |> | |> |I bought one of those about 12 months ago and it is perfect for winding |> |up the landlord of my local real ale pub. The one thing he hates is to |> |be told that is serving his beer at the wrong temperature. A quick pull |> |of the trigger and he is convinced. |> |> Surely it measured the temperature of the outside of the glass not the |> temperature of the beer ;-)

I would use my probe thermometer

|LOL Yes. But since the glass is only a container that is quite thin, the |contents will be equal to the outside of the glass.

Glass is far from a perfect conductor of heat so the outside surface glass will be higher than the beer.

As I *hate* beer, this is just of casual interest.

Sea level standard is ISA 15 deg. C and a lapse rate of 1. 98 deg. per

The message from "jaycee" contains these words:

The adiabatic temperature drop I remember from my school days more than

A quick google led me to Wikipedia (I wonder why:-)) and an article that purported to explain the differences between Environmental lapse rate (1.99 degrees C/1000 ft), Dry adiabatic lapse rate (3/1000) and Moist adiabatic lapse rate (1.51/1000).

ISTM that on the basis of that article 3 degrees per thousand feet should be the figure to use to determine the temperature drop between ground and cloud.

| |crb wrote: |> Andrew Gabriel wrote: |> > No, I get believable readings from clouds, typically -40 to -50, |> > which agrees with what aircraft report as the outside temperature. |> >

|>

|> Clouds at -40 to -50? - I don't think so. You have to go to around |> 30,000 feet or above to get down to those temperatures. |>

|> CRB | |Sea level standard is ISA 15 deg. C and a lapse rate of 1. 98 deg. per |1000' you can work it out for yourself? Although in different parts of |the world the altitude temp does not always follow the formulae.

I would believe -40C to -50C the IR thermometer might not *see* the clouds, but something else far higher.

The message from Dave Fawthrop contains these words:

If anyone remembers Daedalus and Dreadco in the back of New Scientist many moons ago, the author suggests using reflectors to radiate heat into the blackness of space, since at night it's a nice low temperature

- perfect for the cold end of a heat engine using solar stored from the previous day as the hot end. Not an entirely stupid idea.