Outside Temp Gauges

essex-commuter

I have two digital 'weather stations' with wireless outdoor sensors. Both units (different makes) showed a temperature of minus 1.5 when I left this morning. I thought it felt about minus 1.5 too. As all 5 of my closest colleagues arrived in work they announced how cold it was etc etc, and then stating what temperature the car said. Two of my colleagues live within 0.5 miles of my house, one said their car was showing minus 5, the other said minus 7.

Any ideas why my sensors seem innacurate...or could they be correct? The sensors are outside (obviously) and not near any heat source.

Funny hwo everyone comes in work moaning about the cold...they walk from their front door to their car door and then 20 metres from their car to the office...and their friggin' meteorological experts!

mudcow007

i dont trust car temp sensors, they are generally not that far away from a hot engine

plus they get full of crap off the road making them iffy

i would say your temps are more likely to be accurate

also, are you temp gauges protected by the wind? near a wall?

could be loads of reasons for variations in readings, i would have though

rubertoe

I assume that those in cars are moving?

This will lower the temperature as opposed to a static sensor.

cornerblock

essex-commuter wrote:

I thought it felt about minus 1.5 too.

None of them so expert as you though hey? Not 1 or 2 then?

peat

The ones in cars are conflicted between wind-chill and engine heat. So i too am skeptical.

I have a little cheapy alcohol one blu-tacked to the outside of my window. Bedroom window. Its a good indicator, but i accept that it may be affected by thermal loss through the windows.

essex-commuter

Cornerblock wrote:

essex-commuter wrote:

I thought it felt about minus 1.5 too.

None of them so expert as you though hey? Not 1 or 2 then?

God no, it was nothing near minus 2

BigLights

i also have one of those weather stations - it's usually bang on par with the weather forecasts when above zero, but it's reluctant to ever get below -2/-3...even when the forecast is below that. It may be that they're just not that great at very cold temperatures? No idea.

I'm also a skeptic re car thermometers - they're just a very rough guide.

veronese68

essex-commuter wrote:

Cornerblock wrote:

essex-commuter wrote:

I thought it felt about minus 1.5 too.

None of them so expert as you though hey? Not 1 or 2 then?

God no, it was nothing near minus 2

Mine was showing -3.6, none of these half measures and approximations for me. Car showed -2.5 though.

bobbygloss

I think location of the sensor is very critical. In the afternoons our outside sensor catches the sun and can be showing +15C when there is still ice on the car. But early in the morning it seems to be quite close (-11.1C on house wall compared to -10.5C in the car yesterday).

jds_1981

Peat wrote:

The ones in cars are conflicted between wind-chill and engine heat. So i too am skeptical.

Wind chill eh? You know that is just the effect that air flow has on bringing something to ambient temperature?

meanredspider

To get some calibration, go onto www.wunderground.com and find your location. With luck there will be plenty of weather stations near you and you can click on them to see the temperatures any time in history that they were recording (including, of course, this morning when your reading was -1.5C). These stations are typically home-operated £400-£1000 things connected to the web. I find them really useful. They usually agree with my Oregon Scientific remote sensor within a degree.

I find car gauges resonably close (+/- 1 or 2C).

When it's very cold, the air tends to be very still and you get massive local effects because the only thing moving the air is it's density so cold air sits in the gullies. My commute has lots of dips and troughs and you can feel it as you move through. I also know that my side of the Black Isle is often 3 or 4C colder than Inverness which has its own microclimate caused mostly by the water.

itboffin

Mine said -1.5 however judging by the burning cold blocks of ice that used to be my hands I think it might have been a lot colder.

I almost for a minute didn't take the cx with ice tyres, that would have been a big mistake

meanredspider

itboffin wrote:

Mine said -1.5 however judging by the burning cold blocks of ice that used to be my hands I think it might have been a lot colder.

I almost for a minute didn't take the cx with ice tyres, that would have been a big mistake

Again, going by Wunderground, it looks as though it was about spot-on at -1.5

Why wouldn't you have taken the ice tyres when it's below freezing? I find I need to use mine at anything below around 1C ambient at the time I'm leaving to be sure of not finding ice on the route.

Dog Breath

rubertoe wrote:

I assume that those in cars are moving?

This will lower the temperature as opposed to a static sensor.

No they don't. Temperature sensors are unaffected by wind chill. They measure the ambient air temperature which is the same no matter what speed you are doing.

If the OP has a calibrated temperature sensor then I would say this would be more accurate. Incidently what model are you using. I did consider buying a Davis VP2 weather station from Prodata

essex-commuter

Dog Breath wrote:

Incidently what model are you using. I did consider buying a Davis VP2 weather station from Prodata

Nothing fancy, just something from Oregon Scientific. The fact that my 2 seperate gauges show the same temperature when the sensors are together indicates that they are accurate and if they are both wrong it is probably due to the location of the sensor which is outside, near but not attached to a wall of the house and not afffected by any heat source that I am aware of.

Kieran_Burns

I've been trying to find a replacement outside temp sensor (the actual sensor wire itself) as I'm convinced mine is completely borked.

It's been showing something like +2C when I know it's been well below freezing

Fireblade96

I spent a whole £3.99 on one of these

which told me it was -2.5 this morning. My nose-ometer reckons that was pretty accurate.

In other news, the cleaners at work have just warned me it's snowing quite heavily, so I'm glad I've got the MTB.

Sharkyssurfers

essex-commuter wrote:

I have two digital 'weather stations' with wireless outdoor sensors. Both units (different makes) showed a temperature of minus 1.5 when I left this morning. I thought it felt about minus 1.5 too. As all 5 of my closest colleagues arrived in work they announced how cold it was etc etc, and then stating what temperature the car said. Two of my colleagues live within 0.5 miles of my house, one said their car was showing minus 5, the other said minus 7.

Any ideas why my sensors seem innacurate...or could they be correct? The sensors are outside (obviously) and not near any heat source.

Funny hwo everyone comes in work moaning about the cold...they walk from their front door to their car door and then 20 metres from their car to the office...and their friggin' meteorological experts!

well im from around your parts and according to my garmin i was riding in -7 in canvey and -7 through romford

meanredspider

Sharkyssurfers wrote:

well im from around your parts and according to my garmin i was riding in -7 in canvey and -7 through romford

http://www.wunderground.com/weatherstat ... =IESSEXCA1

Wunderground would agree..

My Garmin reads low though

iwearshorts

-4.7 in North London this morning, which was a record so far for 2012 - 13 8)

Love my weather station. What it reads in the morning will decide what I wear on my commute.

It even predicts snow fairly reliably!

jamesco

mudcow007 wrote:

i dont trust car temp sensors, they are generally not that far away from a hot engine

My motorbike displayed +1 when I left work at lunchtime today and a rather more balmy +9 by the time I got home. Where it began to snow...

itboffin

meanredspider wrote:

Why wouldn't you have taken the ice tyres when it's below freezing? I find I need to use mine at anything below around 1C ambient at the time I'm leaving to be sure of not finding ice on the route.

Because this mofo hill http://app.strava.com/segments/783599 the 1st mile climb makes me sad at 6.30 in the morning dark & cold with a MASSHOOF rucksack, added the CX with studded tyres is the final kick in the balls.

Nice view from the top mind esp the bright burning red thing I think they call "the sun"

pdw

Sharkyssurfers wrote:

well im from around your parts and according to my garmin i was riding in -7 in canvey and -7 through romford

My Garmin under reads significantly at low temperatures. I've got a thermometer outside my window wired into a computer (so I can check the temperature from my phone before I get out of bed ) and that correlates very well with both local weather stations and my car. The Garmin reads at least 2-4 degrees lower when it's cold... unless you keep turning the backlight on.

gosport_commuter

meanredspider wrote:

To get some calibration, go onto http://www.wunderground.com and find your location. With luck there will be plenty of weather stations near you and you can click on them to see the temperatures any time in history that they were recording (including, of course, this morning when your reading was -1.5C). These stations are typically home-operated £400-£1000 things connected to the web. I find them really useful. They usually agree with my Oregon Scientific remote sensor within a degree.

I find car gauges resonably close (+/- 1 or 2C).

When it's very cold, the air tends to be very still and you get massive local effects because the only thing moving the air is it's density so cold air sits in the gullies. My commute has lots of dips and troughs and you can feel it as you move through. I also know that my side of the Black Isle is often 3 or 4C colder than Inverness which has its own microclimate caused mostly by the water.

Thanks for that site, awesome data sets and confirmed for me that give or take half a degree my outside thermometer is near spot on! Also gives me an easy way to check the outside temp before my evening commute home without pestering her indoors with requests.

dodgy

+1 on the recommendation to use Wunderground data, I usually check on the local stations before heading out to get an idea of the actual temperature and what I know to be effective clothing in those conditions.

On wind chill, you always see this, but just to be clear - Wind chill doesn't make the air colder, the ambient air temperature is the ambient air temperature. Just because you start moving forward or the wind increases to 1000mph, the air temperature is still the same. Wind chill is the sensation of the air feeling cooler at higher speeds because of the chiling effect on skin due to evaporation (mostly).

In real terms, you as a flesh and bones person will move towards ambient air temperature more quickly due to wind chill, but you (or your bike) will not and can not go below ambient air temperature.

Sorry 8)

dodgy

PS, here's a link to Wunderground's large map, at a glance you can see actual temperatures.

http://www.wunderground.com/wundermap/? ... 06&zoom=13

veronese68

I was driving home last night and when I left work the car showed -0.5c. i dropped a colleague off that lives just outside Bushy Park and the temperature was reading -2c. By the time I got to the kingston one way system it was reading +1c. This is all in the space of about 5 miles.
I know the park is a lot colder than the surrounding areas, but I didn't think it was quite so much difference. I know it also gets colder as you go further into the park. I've seen puddles just inside the perimeter, but when you get further in they are frozen solid.

meanredspider

Veronese68 wrote:

I was driving home last night and when I left work the car showed -0.5c. i dropped a colleague off that lives just outside Bushy Park and the temperature was reading -2c. By the time I got to the kingston one way system it was reading +1c. This is all in the space of about 5 miles.
I know the park is a lot colder than the surrounding areas, but I didn't think it was quite so much difference. I know it also gets colder as you go further into the park. I've seen puddles just inside the perimeter, but when you get further in they are frozen solid.

It's not uncommon - especially when it's quite still