Temperature Readings: PE2 vs Herpstat Probe

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Temperature Readings: PE2 vs Herpstat Probe

Postby TallyReed » Sun May 19, 2019 4:55 pm

Having just set up the new enclosure, I will run it for a week or so to ensure that everything is working properly before picking up our new dragon.

I have an Exo-Terra 150W Daylight Basking Spot in an Exo-Terra Light Dome mounted over log which angles upward to a ledge, with the bulb being 8-9" above the lamp at its closest (the ET site notes the bulb should reach 109 @ 8"). I have the lamp controlled by a Herpstat 4 with the lamp set to Heat (Dimming) and basking assist enabled. I have the temp set to 104 and the probe consistently reads 104.

I also picked up a Pro Exotics 2 temp gun, but when I measure the temp directly beside the Herpstat probe, it reads anywhere from 109 - 115.6 measured from about 4". I have never used a temp gun before and the instructions with the PE2 don't offer anything regarding calibration.

If it was only a degree or so difference, I wouldn't be concerned and given that I keep getting different readings for the same spot with the PE2, I am inclined to rely on the Herpstat probe.

Anyone have experience using these two pieces of equipment, who might be able to offer some insights?
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Re: Temperature Readings: PE2 vs Herpstat Probe

Postby kingofnobbys » Mon May 20, 2019 1:57 am

Had to look the gun up. http://www.ultimaterc.com/reviews/pro-e ... n-pe1-pe2/
Specs
Image

The Habistat probe will be accurate , you can improve the accuracy of the readings from the PE-2 but you need to know :
1) the exact material in the basking spot (so you can get the correct emissivity for that surface and material, this will make a noticeable difference.
2) get the measuring technique right , be careful of specular errors.

Refer to these for more information :
refer to information : viewtopic.php?f=34&t=239064&p=1833542#p1833542
and this explain more : viewtopic.php?f=34&t=241233

It is possible to compensate for emissivity errors but the calculations involved will be beyond most reptile keepers who don't have the necessary physics or engineering education , the existing IR gun is likely 20 to 30 degrees Celsius out when reading the surface temperature the "NON STANDARD SURFACE (which has a emissivity significantly different to the standard e (gun) = 0.95 found with cheap IR guns who have no emissivity adjustment).




The brief explanation is as follows : the Stefan-Boltzmann Law gives the radiated infrared energy emitted by a target surface and shows this is exponentially related to the absolute temperature of that surface.
The equation is E_b = εσT^4 where ε is the surface emissivity and the true surface temperature is calculated using this equation
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Re: Temperature Readings: PE2 vs Herpstat Probe

Postby TallyReed » Mon May 20, 2019 4:58 am

Thanks, appreciate the info. I will try adjusting the emissivity level, guessing at the type of wood (hard and dense - likely some type of ash) and give it another go, making sure I measure correctly.

Cheers, James.
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