Laser pyrometer accuracy & other questions

[Turbo6Smackdown]

This is a technical question. Maybe someone like Richard Clark or Mr. Roland could chime in.
Question 1. How inherently accurate are homeowner grade, or consumer grade laser pyrometers from the factory? Are they close? 2. How off are the readings if I shoot different mediums/substrates? E.G. a down pipe or radiator hose. Am I to presume that the temperature differential is different from material to material? By that I mean that if I shoot a rad hose, and it reads say 175, how far off is that from the actual coolant flowing within? Does the air temp in between the pyrometer and the actual surface modify the readings at all?
And what about air temps inside a down pipe. If I shoot the surface, how far off is the reading of the surface different from the actual exhaust gasses passing inside?

I ask because I'm interested in using it for data collection for logging personal results from modifications like brake rotors, coolant lines etc., but I'm not going to spend the money if it's not accurate. I know that lasing a brake rotor is pretty cut and dry, but not soo much when you're trying to determine the actual temp of a fluid beneath a surface. What say you?

 

[dank GN]

I have a laser temp gun and used to work as a environmental test tech testing aero space components . Mine was in calabriation according to the manufacture specs .

 

[Turbo6Smackdown]

Of course it's going to be lol. They wouldn't purposely ship instructions that would show otherwise would they?

 

[dank GN]

I guess what I was trying to say is mine is within 4* at 3'

 

[Turbo6Smackdown]

I see. Now how do you check the actual coolant temp inside a coolant hose? How far off is the differential?

 

[dank GN]

The only thing I can think of is to put a thermocouple in the hose . I'm not sure what the differential would be between the inside and outside of the hose . Do u not trust your readings? Take a temp on the inlet of the radiator and on the outlet with your inferred temp gun

 

[Turbo6Smackdown]

I just don't know to trust the readings of fluid through another material with a pyrometer. I'm just curious. I'm actually more curious of the air temps inside the downpipe versus the temp of the outside of the tubing of the downpipe itself.

 

[SHADOWII]

You can use the gun for reference. The cheaper units have to be placed closer to the object for accuracy. You could create a chart for your normal operating conditions, where under load, those operating temps are going to change dependent on conditions. Nothing will work as well as the thermocouples, as they will change with the conditions. But for troubleshooting purposes, when normal operating temps are known, can be helpful.

I just don't know to trust the readings of fluid through another material with a pyrometer. I'm just curious. I'm actually more curious of the air temps inside the downpipe versus the temp of the outside of the tubing of the downpipe itself.

I've used pyrometers for years, and if you are using the "K" type which most are rated @1600-2100*, if I remember correctly, you would be operating in the mid-range which will give longevity to the probe.

 

[delcowizzid]

$22 bucks you can measure the temp in the dump or do as i do measure before turbine in an exhaust runner 2 inches from the head either middle cylinder is good they run the hottest.i modded my gauge and added 0-5V logging output so i can datalog http://www.ebay.com.au/itm/2-52mm-U...U_Car_Parts_Accessories&hash=item5af848896a#1

 

[delcowizzid]

or if you have a good multimeter with temp setting buy a k-type thermocouple and bung off ebay and the meter will display temp

 

[dank GN]

I have one that I used for years now I'm recordeding it on my PL with a diffrent KType TC

for sale BTW

 

[earlbrown]

The material won't really change the readings that much. Now shining it one something highly reflective will make it read artificially low.


What you were talking about with trying to find fluid temps from the outside will depend on three things, mass of the fluid, mass of the pipe, and environmental conditions. If you're measuring a heavy, thick walled pipe with a blower hitting it, that will read lower than a thin walled pipe with static air around it. What I'm getting at is if the pipe has time and opportunity to stabilize with the fluid inside. If they can 'match', then you can get a fairly good reading.

 

[Raeban]

The material won't really change the readings that much. Now shining it one something highly reflective will make it read artificially low.


What you were talking about with trying to find fluid temps from the outside will depend on three things, mass of the fluid, mass of the pipe, and environmental conditions. If you're measuring a heavy, thick walled pipe with a blower hitting it, that will read lower than a thin walled pipe with static air around it. What I'm getting at is if the pipe has time and opportunity to stabilize with the fluid inside. If they can 'match', then you can get a fairly good reading.

Not much that can be added to this but the bottom line is the infrared gun makes a major assumption, and should tell you on a sticker/screen what emissivity it is assuming. Typically this is 0.95 or there abouts. If you read a material that has a significant difference in the calibration emissivity you will get inaccurate results. Earl's example of a shiny metal is a very low emissivity which is why typical off the shelf infrared measurements aren't used. Dull dark metals and even the rubber hose example you mentioned above are usually fairly close to 0.95 so repeatable results are common.

 

[earlbrown]

^yep. Nice cold beers cans usually read in the 60's whey they are much colder.


it's also fun to go outside when it's 100F out and point them up at the sky. you can tell a major difference between a cloud and outer space

 

[Raeban]

^yep. Nice cold beers cans usually read in the 60's whey they are much colder.


it's also fun to go outside when it's 100F out and point them up at the sky. you can tell a major difference between a cloud and outer space

LOL!