Renix overheating IR temp testing

Bought my daughter a Northern Tool (NT) "General" brand hand held Mini IR temp tester for Christmas. Compared the readings on it to my Harbor Freight (HF) 10 year old one, with the battery it had and again with a new battery.

The new battery raised the temp readings about 3 degrees testing my had-skin temp later, but the NT unit read about 96-97 F testing my hand last night and the HF unit read 86 with the used battery and still only 93 at most with a new battery.

The radiator and T-Stat housing tests with both brands IR testers read consistently 20-30*F lower with the HF tester than with the NT tester all the way from 150*F to 210*F. Bother are very similar specs, design and size.

I find that very disturbing. Has any one else here ever checked the different brands testing their jeep radiator and T-Stat temps?

I am inclined to think the real temps are in between the readings I was getting with both testers on the Jeep last night, but testing the skin temp of my hand says the new NT-General brand was damn close for skin surface temp out doors in the cold, reading 96.8 IIRC.

Just tested the inside of my mouth with the HF one and got 96 F, so it is not way off there in that range (new battery), but it read like 175F on the T-Stat last night when the NT-General brand was reading 200*F. My HF has IIRC always read about 180 F in the test conditions I had last night that read 200 F with the NT unit.

????? On the same exact spot. I repeated tests for about 45 minutes about 50-60 times with both testers.

I may need to try the HF with the new Battery again and confirm the numbers, but I no longer have the NT unit, as my daughter headed back to college up state with it.

https://www.fluke.com/en-us/learn/b...et-great-results-with-an-infrared-thermometer

Lots of variance in these and how they read. I've never tested mine. I usually just use it to compare readings and less for an absolute Temp.

Does it show your inside walls inside the house close to what you're got the thermostat set?

lawsoncl said:

Does it show your inside walls inside the house close to what you're got the thermostat set?

Click to expand...

That is a loaded question. No as the house is very VERY old, very drafty, poorly insulated, etc. But I have used it for 10 years, and get pretty reliable/reasonable numbers in the house, floors, walls, ceiling, near the window AC unit.... all make sense. 70-85* F range.

Its the 20+ degree F span difference at the 150-200 F range between the two that got my attention last night. If I get bored someday I might use boiling water (at sea level) and ice cubes in water to see how close to 32 F and 212 F it gets.

You can do a simple test, use a thermal interface material (thermal grease) and a fever thermometer. Compare the results.

Check the product destructions for the optimum stand off distance, Clean the lens with alcohol. Matt surfaces seem to work better than reflective surfaces.

My IR tester is just a quick check. I have a thermo couple contact surface temperature tester, along with heat paste, that gives way more exact results.

My VOM also has a temperature scale and a thermal couple. Along with a dab of thermal paste it gives good readings.

Electromagnetic fields can also mess up IR readings, learned that one checking bearing temperature on large pumps, large electric motors etc.

True surface temperature, with a contact type tester works way better, IMO. Heat paste also helps when you need a more exact temperature.

Lots of good information already here. Another example to show the limitations of IR thermometers is pointing it at the HVAC vents in your car. It will not give a consistent reading over a period of time. I just stick a wire thermocouple in the vent.

I have had even worse luck with surface contact thermocouples.

Many surfaces are no physically reachable for contact testing while they can tested with IR.