Reliable min/max thermometer

[greenishfing]

At the start of the year I had 2 min/max thermometers for the greenhouses at the allotment. One was an old mercury type that you had to shake to reset. (it came free with a secondhand greenhouse). I eventually shook it to destruction.

The other is one of these type:

which I was a bit sceptical about as I had thought some of the min readings were a bit low. This morning it said last nights min temperature was -6˚. I know it was cold but it was not that cold.

When I started this thread I was going to ask if anyone could recommend a reliable min/max thermometer (without breaking the bank) but now I am wondering do I need one? Do I really need to know what has already happened?

[Bigmallly]

I picked up one of these from H0mebase but they are cheaper on Amzon:

http://www.amazon.co.uk/Large-Thermo...ax+thermometer

[polc1410]

Do you need a thermometer? Interesting question. Of course you do. Its technology and we all need technology... Don't we?

Seriously knowing what happened doesn't fix a frosted squash. But there are a number of things you might want to use it for...

- look at forecast min, measure actual min, check reported min. Provided you trust the numbers you understand your local temp in GH relative to forecast and actual. If that's 2C higher than forecast you know next time its fore last 8C you can hope for 10C.
- check if heating is reversing the minimum
- check if ventilation is cooling it enough
- check ventilation not too much

Some of those will be less critical for precision than others. Personally prefer digital with inside and outside probes...

[Sheffsteel]

Excellent points from pol1410,

It's not just the information (temperature reading) that's important, it's all about how you use and learn from that information.

I recently bought 10 white max/ min digital thermometers from GreenhousePeople. Seemed well made and each thermometer came with a Duracell battery. Lined them all up outside in the same place to check if they would give the same reading for accuracy, returned 15 minutes later and was disappointed to see a 2 degree swing between the max and min current temperature reading. The specifications say the thermometer are accurate to within 1 degree.

However another 30 minutes later I checked the readings again and this times they were more identical with a 0.7 degree C swing between the max and min reading. So the quoted within 1 degree accuracy does seem correct.

I was previously thinking about buying a a full weather station but an excellent and FREE alternative is the IPad app called WUNDERSTATION from Weather Underground.

There are 10,000's of weather stations around the world sending current data to this app.

There is a private amateur weather station on the same road where I live sending readings every 5 minutes regards rain, temps, humidity and wind speed.

There are various detailed graphs showing historical records and also weather forecasts.

The only problem is you don't know how the private amateur stations are set up and can't 100% guarantee their accuracy. Therefore I cross reference their data with my thermometers and it does appear very accurate.

I've no need to buy a weather station now because I'm using current data from dozens of other stations within the city.

[Martin H]

Hi Sheffsteel,

Welcome to the vine!

Good summary. I like Wunderground for local forecasts. They seem pretty accurate for me, despite that I live at the bottom of a valley while the local amateur stations are higher up.

What it can't tell me is what's been happening inside my greenhouse. I love my wifi logger!

[Bigmallly]

Thanks for the Wunderground info Martin............Great site.