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Pyrometer questions?

Discussion in 'Technical Q&A' started by Scotty, Sep 25, 2005.

  1. Scotty

    Scotty F1 Veteran
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    I am thinking about getting a pyrometer (or two) and have some specific questions.

    1) Regarding infrared (non-contact) pyrometers, how important is adjustable emissivity (I will use this to quickly check tire temps, brake disk temps, as well as an assortment of around the house tasks)?

    2) When I've read on the subject, most folks feel that non-contact pyrometers are significantly inferior to pin type contact pyrometers in terms of checking tire temps after track runs. Does anyone have any input regarding a good brand, model number, etc?

    Thanks--Scott
     
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  3. bwassam

    bwassam Formula Junior

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    There's some stuff in the archives about this. I don't have the address.

    Bob Wassam
     
  4. Scotty

    Scotty F1 Veteran
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    Bob--I'm happpy to admit that I am search impaired--but I did search--there are some threads about what to do with the results from pyrometer testing, but not anything that would specifically answer my questions.

    But if there is thread that I missed--I will throw myself at the alter of shame.
     
  5. steve f

    steve f F1 World Champ

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    whats a pyrometer ????????
     
  6. cavallo_nero

    cavallo_nero Formula 3

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    I mounted a pyrometer in my carb 308 (it measures exhaust temps at the cylinder head) - good for tuning purposes. works great!! i used the existing header probe nipples that are on my euro 308
    john
     
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  8. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Scott -- I think you answered your own question in that the downside to a non-contact pyrometer is that either the device or the operator has to "know" the emissivity of the thing being measured (so if you buy a "non-adjustable" one you get some sort of internal default value for emissivity). If you really needed decent accuracy out a non-contact version, I think you'd have to use a contact-type version on the same sample of interest so that you could learn/calibrate the (adjustable) non-contact one (and then assume that when measuring similar samples with the non-contact pyrometer that the emissivity is the same) -- JMO.
     
  9. Scotty

    Scotty F1 Veteran
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    Pyrometer = device for measuring high temperatures.

    Non-contact--uses infrared emissions to estimate the surface temperature of an object. Automotive uses include exhaust system temps (are my TR cats clogging?) as well as brake disk temps (did the ducting I put in lower temps on the track? or at what temperature do these pads start to fade?). Convenient 'cause you don't have to touch what you are measuring.

    Contact--uses some kind of a probe to measure either surface or internal temp. In my case, I am interested in tire temp measurments--and would use a pin type probe that you stick in the tire tread to get the carcass (as opposed to surface) temp of tires run on the track. Useful to evaluate air pressures, as well as to know what part of the tread is doing most of the work.

    "91tr" I found an IR pyrometer that also has a contact probe and adjustable emissivity--thus it can be "self calibrated". Although, in most instances, I'm more interested in relative temperature differences as opposed to absolutely accurate numbers.

    Any thoughts on a good tire pyrometer?
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
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    No
     
  11. bill308

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    For tire temperature measurements, emissivity corrections are not real important. This is because you are interrested in the relative temperatures across the tire width and camparing temperatures from tire to tire. Since all the target temperatures are the same material and surface finish, error due to emissivity will be negligible. For tire rubber, an emissivity of 0.9 is about right though.

    Emissivity can have a significant effect on some surfaces, especially highly polished ones which have very very low emissivity values. Polished aluminum has an emissivity of about 0.04. In this case, the instrument will measure a lower temperature than actual. In fact, only a true black body will achieve an emissivity maximum of 1.0.

    At work we use Flir infrared cameras to image PC boards for hot spots and trouble shooting purposes during development testing. These cameras, about 60k each, are military grade and you can see area gradients to a fraction of a degree. Even in this kind of work, absolute errors of 1-3 degrees are seldom important. We almost always assume an emissivity of 0.9, which works well for all components except metal ones. If the surface is very shinny, what one really sees is a reflection of the surrounding ambient.

    My recommendation is to set emissivity to 0.9 for tire work and painted surfaces and use the measurements directly. By the way, the color of paint has almost no bearing on the measurement. This is because color is in the visible spectrum and the bulk of heat transfer occurs in the infrared region which the human eye cannot see.
     
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  13. Dubai Vol

    Dubai Vol Formula 3

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    Exactly. The goal in tire temp measurement is to do them as fast as possible before the temps equalise, which is why I like an IR non-contact gun for this application. With a probe you have to wait a lot longer for the temp to reach true value, and all the while all your other temps are averaging themselves out. Ideally you have twelve guys with 12 IR guns hanging over the pit wall measuring inside, center and outside temps on each tire as you exit the last corner. Settle for you to measure and your pit bunny to write em down. (Rem when girlfriends did timing and scoring? A reason to hate transponders if you ask me) Fancy pyrometers will record the temps but that's for sissies :p

    But it's a good point that for almost any app it's relative temps that matter so a small absolute error from emissivity is not really important.
     
  14. Scotty

    Scotty F1 Veteran
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    Thanks for the input. I am going to purchase a Mastercool #52225. This unit is cool (I hope) because it is an infrared pyrometer that has adjustable emissivity and a lock mode to capture temp readings. Not such a big deal there, but it also has a K jack that allows attachment of a variety of thermocouples (contact temp. measuring devices). It comes with an immersion probe (so I can check the temps of my syrah or espresso) but the Longacre tire probe (according to the company) should also work just fine. So the Mastercool is about $80 on the web, plus about $70 for a tire probe, and I have a multifunction device. I'll report back after I've tried it to let everyone know how it works.
     
  15. fatbillybob

    fatbillybob F1 World Champ
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    Search longacre tire pyrometer
     

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