Obtain an accurate thermometer?

[Fredsie]

Hi

 

I expect this has been discussed before but I can't find anything pertinent via search.

 

I have had a number of thermometers over the years and clearly there is always a bit of variation in what each registers in the same situation. Recently made digital thermometers show a reading to 0.1C but clearly this is very different to having an accuracy to that level. 

 

So my question is, how do I really know what the air temperature is in my back yard? Is there some way of obtaining a calibration of a thermometer (so that I at least know what offset to use), or is there a thermometer I can buy that really is this accurate?

 

Cheers

 

Fred

[Paul]

Hi Fred, just moving this over to the weather stations forum where I think you'll get more response. 

 

What I would say is that it's not just about the thermometer - it's about the environment you put it in - ie you'll probably need a Stevenson screen or similar to stop it being affected by sunlight etc. 

[Fredsie]

OK thanks.

 

I understand the issues around the siting of thermometer equipment. In my question I suppose I was putting the issue the other way round: one might ask what's the point of getting an expensive Stevenson screen etc if you can't rely on what the thermometer reads? 

[Terminal Moraine]

Hi

 

I expect this has been discussed before but I can't find anything pertinent via search.

 

I have had a number of thermometers over the years and clearly there is always a bit of variation in what each registers in the same situation. Recently made digital thermometers show a reading to 0.1C but clearly this is very different to having an accuracy to that level. 

 

So my question is, how do I really know what the air temperature is in my back yard? Is there some way of obtaining a calibration of a thermometer (so that I at least know what offset to use), or is there a thermometer I can buy that really is this accurate?

 

Cheers

 

Fred

The only way I know of, Fredsie, is to get an NPL ( National Physics Laboratory) certificate for your thermometer(s) but they are very expensive. If memory serves me well I think around £100 per thermometer the last time I enquired.

If you buy standard glass sheathed thermometers from a reputable company they are generally accurate to within 0.2c which is as good as you can hope for and well within the margin of error likely to occur from the specific peculiarities of your site.

Good quality digital thermometers usually have a stated accuracy of 0.2c ( for the best ones) to around 0.5c around the middle of the market.

Alternatively, if you know anyone with a Met Office certified station their thermometers will be checked against the Met Office's inspector's thermometer every 3 years and should be accurate to within 0.2c. 

[Fredsie]

Well 1/5 of a degree accuracy would be more than good enough for me!  I don't know of any certified stations but if I can get hold of a thermometer that's likely to be right within 0.5 C I'd be happy. It seems from what you're saying I should be able to get either glass or digital kit which will do this fairly easily? Did you have any particular examples in mind?

[Terminal Moraine]

Well 1/5 of a degree accuracy would be more than good enough for me!  I don't know of any certified stations but if I can get hold of a thermometer that's likely to be right within 0.5 C I'd be happy. It seems from what you're saying I should be able to get either glass or digital kit which will do this fairly easily? Did you have any particular examples in mind?

There are so many digital sensors on the market it's a case of Googling 'Meteorological temperature sensors' or something similar and then trawling through the results to find something that suits your needs.

With regard to glass thermometers before my station became a Met' Office site I used to get mine from Munro Meteorological or Casella but having just looked I see that Casella now only seem to deal in high end electronic equipment and Munro list only minimum thermometers for some reason. 

[The PIT]

You won't be able to buy any accurate thermometers due to the mercury being banned. Slowly accurate digital versions will come and I will be investing in some new equipment shortly.