NZ Weather Forum

Had a nasty surprise yesterday driving Tahuna Road towards Galatea from Te Teko, it's a quiet road, with an outside air temp of 6°C according to the car I wasn't too concerned about ice despite quite a good frost. Wrong, luckily I wasn't going that fast, but I still had a bit of correcting to do. Was interesting observing the differing temperatures as I headed South and gained altitude. Am now thinking I need to check the cars thermometer against the Kestrel and see what it's accuracy is.

tgsnoopy wrote:Had a nasty surprise yesterday driving Tahuna Road towards Galatea from Te Teko, it's a quiet road, with an outside air temp of 6°C according to the car I wasn't too concerned about ice despite quite a good frost. Wrong, luckily I wasn't going that fast, but I still had a bit of correcting to do. Was interesting observing the differing temperatures as I headed South and gained altitude. Am now thinking I need to check the cars thermometer against the Kestrel and see what it's accuracy is.

In a word poor, car thermometers aren't very good with temp flacuations. Partly because they are attached to a ton and a half of metal and also because they are cheap thermometers. Kestrels on the other hand are top quality. Unless you break the battery compartment and water gets in, that killed mine. Lasted a good 4 years though.

That might have been true initially Tim, but modern cars, whilst moving could and in my opinion should have quite accurate thermometers these days.

All it would take is a LM335 temperature sensor, 2 resistors and a capacitor into a A to D port on a micro and it could be very accurate.

In any case, till them the thermometer seemed to be quite accurate in the 15 to 25° range at least. Now I'm thinking it may be reading high in the lower range. It'll be an interesting exercise seeing how accurate it is.

Re the Kestrel, I just had my battery compartment cover break. But as I'm aware it is an issue (gee that spring is over the top tension wise), I had a spare ready Not sure who gave me the heads up, Maybe Willoughby or you?

I don't have vehicles that have car thermometers but when we hired a car when we were in England 3 years ago which has a display of the current outside condition, but then I thought are they really accurate?
Are they? How can you get a reading when you are moving along?

they seem pretty accurate to me once there has been some air flow around them for a couple of mintues

I think for the most part there fine but will read high once a hot car has been sitting for a while and I find ours reads high when following lots of cars up the likes of porters pass.
I find ours matches up exactly with our weather station at any point.

Since I started my new job in Parnell just over a week ago I've noticed my car thermometer is actually a fairly good guide to the outside temperature. I guess it won't be quite as accurate in summer with the hotter roads though.

Our captiva thermometer is always spot on ( albeit it rounds to the nearest .5)

Yeah they will be in winter as the road surface doesn't give off much if any heat. But your car is made of metal and a lot of it, if you are moving airflow would highly negate the fact the car takes a while to heat up cool down, ie large thermal mass. But once you start moving up and down hills in and out of valleys it wont really change much. Maybe 0.5c to 1c whereas the actual difference in air temp at 1m above the surface could vary by 5c maybe more. Quite problematic if you car temp says 5c whereas it is actually below 0c.

I have done a lot of driving as a passanger and driver and I pretty much watch the temp gauge continously (of course i look at the road too!). Drives my wife mad when I update her when it changes!

tgsnoopy wrote:That might have been true initially Tim, but modern cars, whilst moving could and in my opinion should have quite accurate thermometers these days.

All it would take is a LM335 temperature sensor, 2 resistors and a capacitor into a A to D port on a micro and it could be very accurate.

In any case, till them the thermometer seemed to be quite accurate in the 15 to 25° range at least. Now I'm thinking it may be reading high in the lower range. It'll be an interesting exercise seeing how accurate it is.

Re the Kestrel, I just had my battery compartment cover break. But as I'm aware it is an issue (gee that spring is over the top tension wise), I had a spare ready Not sure who gave me the heads up, Maybe Willoughby or you?

Where can you get a spare battery cover from?

But yes as I said in the car thermometer thread. You are right modern cars are a lot more accurate but most models don't give you very good warning of black ice, as you found out! Best system would be a FLIR Forward looking infrared system but I feel that would be distracting! Though I think mercedes have this??

Tim S wrote:Where can you get a spare battery cover from?

At the risk of getting in trouble from Nazi moderators for staying off topic:
http://kestrelmeters.com/products/kestr ... 32-battery
They weren't cheap, I think the two ended up costing me about $25 with shipping.

I find most cars pretty accurate to be honest. Always within a degree once moving for a couple minutes.

I am always watching it and going over high roads like the desert road we play a game "guess how low it will go?"
I always win of course haha.

tgsnoopy wrote:

Tim S wrote:Where can you get a spare battery cover from?

At the risk of getting in trouble from Nazi moderators for staying off topic:
http://kestrelmeters.com/products/kestr ... 32-battery
They weren't cheap, I think the two ended up costing me about $25 with shipping.

Cheers, will get myself one, corrosion is fairly limited so should be mendable.

Now to make this related to frost, Kestrels are very handy for measuring grass temp. Although you do need to leave it for a good 10mins or so to get to the right temp as there isn't any airflow on the ground...

Mine comes up with a warning if it drops below +3c saying warning icey conditions!

Mod Note: Some Posts Merged from Frosts Thread.

shovelopikis wrote:Mine comes up with a warning if it drops below +3c saying warning icey conditions!

I noticed mine flashes for about 10 seconds when it drops from 4 to 3 °C.

Hard to follow this topic as some posts have disappeared / been deleted?? Not worth contributing really...