Memory pyrometer vs. infrared

A while back, there was discussion of the accuracy of probe type tire pyrometers vs. infrareds. Since I have one of each, this last weekend at the Jensenator's christening (still a little fine tuning to go!) I tried them back to back.

Conditions: sunny and dry, 87 degrees ambient, asphalt temp probably ten degrees higher than ambient on average, Hoosier R45 slicks.

Results: the infrared pyrometer read continuously 5 degrees lower than the probe unit. The interesting thing is that this was consistent, i.e. the temp drop/rise at the different measurement points was the same. For instance, a rear tire showing 102/102/102 with the probe was 98/98/98 when measured with the infrared. (Yeah, I nailed the rear tire pressures right off the bat. ) A front tire was (inside to outside) 103/100/98 probe and 98/95/93 infrared. (Got a little camber adjusting to do.) So I guess if (unlike me) you don't have a deep seated almost pathological need to know the temp inside the rubber the infrared will tell you what you need to know so you can get your tire pressures and alignment specs worked out.

Of course all the usual disclaimers apply such as: YMMV, not valid in all states, must be 18 or older or accompanied by an adult, some restrictions apply, will not protect against STDs, liability is restricted to refund of the purchase price, may be unsuitable to some viewers etc etc etc.

Make a ice-water "bath" and let it sit for a little while. Then take the temperature with both. The one taking the 32°F is the one that is correctly calibrated.

^^What he said. Or, boil a pot of water.

Yeah I have both too and as long as you don't mix and match them at the same time, I've seen little problem and good consistency even if they aren't perfectly calibrated.

I can't speak to any other, but both of mine are LongAcre brand. Actually, one of them has the probe "option" with the laser pyrometer. This way I get both in one convenient case.

that is it... the actual temps of your tyres may vary.. but as long as the probe reads the same across the tread.. you are fine.

Slant Six Warmup

I'm partial to IR imagers, myself.

Check calibration in the range of interest. Ice baths and boiling water are good for 0C and 100C, respectively. Use distilled water, and check the effect of your altitude.

For infrared devices, remember to check for reflected energy (What's behind you that might be bouncing infrared radiation off the surface you're shooting) and the emissivity of the surface and the setting on the device. Emissivity of car tires is usually pretty high, but if you're checking other surfaces, you can fool yourself.

Didn't GRM do this exact same comparison a while ago?

infared versus pryometer probe?

mad_machine wrote: ...but as long as the probe reads the same across the tread.. you are fine.

What he said.

RossD wrote: Make a ice-water "bath" and let it sit for a little while. Then take the temperature with both. The one taking the 32°F is the one that is correctly calibrated.

Although I agree... make sure your ice bath uses distilled water for both the ice and the bath... or make sure your boiling uses distilled water at sea level. (or corrected for standard pressure)

You'd be surprised at how much of a difference it makes.