Help with basking rock temp

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bryan
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Help with basking rock temp

Postby bryan » Thu May 23, 2019 4:29 pm

Hey everybody. I’m getting my baby northern baby bluey this upcoming Wednesday so I’m preparing their enclosure for them. Everything is all set up but I am concerned about my basking rock temperature. I use a Philips Par38 flood 45w replacement uses 39w. The dead center of the rock gets to 116F, while the rest of the rock gets around 98F-100F. The hot side substrate gets to 85F-90F. While the cool sides substrate gets to 79F.

Do you guys think this is okay? I measured all of these temps using a temp gun btw. Also I have a Kages enclosure so it’s 4x2x2. Thanks. -bryan
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Re: Help with basking rock temp

Postby mb606587 » Thu May 23, 2019 7:42 pm

Yes you have provided a nice range of temperature gradients for your skink. 116 degree surface temperature seems high to the average person but I assure you take your temperature gun out to the roadway on a hot day and see what it registers. Bet it will be higher than that. My Meraukes bask for hours on 125-135.
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Re: Help with basking rock temp

Postby kingofnobbys » Fri May 24, 2019 1:06 am

Do you know the material the basking rock is made from ?
Can then look up the emissivity and tell you how to compensate the gun temperatures if it's not got the ability to adjust the emissivity setting (and is preset unchangeable at e = 0.95 ).

is the surface of the basking rock smooth or rough / textured ?
makes a big difference ( if smooth and you are not careful you can easily end up reading the temperature of the reflection of the basking globe by mistake).

how big is the gun's spot ratio ?
will be something on the box / package that says 1:8 or 1:12 or something like that .
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Re: Help with basking rock temp

Postby bryan » Fri May 24, 2019 7:10 am

Do you know the material the basking rock is made from? / Is the surface of the basking rock smooth or rough / textured ?
The basking rock i use is a Natural Stone Slate Tile 12in X 12in X 1cm California Gold Slate. I picked out the most smooth slate I could out of the package.

IMG_5419 2.jpg


how big is the gun's spot ratio ?
will be something on the box / package that says 1:8 or 1:12 or something like that .
my temp guns spot ratio is 12:1
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Re: Help with basking rock temp

Postby kingofnobbys » Fri May 24, 2019 8:51 am

bryan wrote:Do you know the material the basking rock is made from? / Is the surface of the basking rock smooth or rough / textured ?
The basking rock i use is a Natural Stone Slate Tile 12in X 12in X 1cm California Gold Slate. I picked out the most smooth slate I could out of the package.

IMG_5419 2.jpg

Emissivity of slate is e = 0.7 , ref https://www.optotherm.com/emiss-table.htm
So you will need to adjust the gun's emissivity to this from the preset value of e(ps) = 0.95

==> instead of reradiating 95% of IR , it only reradiates 70% , so the slab warms faster.

Should have chosen a slate slab with a rougher surface as specular errors with a smooth highly reflective surface like you have will result in errors due to the gun seeing the reflection of the basking globe.

More information .

This explains more : https://www.beardeddragon.org/forums/vi ... 4&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 degree to which errors in emissivity settings will affect temperature and T_error (error in temperature) accuracy even not often understood by many professional physicists , engineers , chemists and thermographers . Little wonder lay people who have no professional training and simply assume the IR gun is going to give accurate temperature readings for all surfaces measured get this wrong .

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
Image




how big is the gun's spot ratio ?
will be something on the box / package that says 1:8 or 1:12 or something like that .
my temp guns spot ratio is 12:1


Make sure the gun is used in such a way that :
>> the emissivity has been adjusted to e = 0.7 (if this option is available)
>> the gun is angled in such a way the light (and IR) from the baking globe is not being reflected into the gun --> will result in a much higher reading
>> Conduct the measurement perpendicular to the material’s surface whenever the emissivity is less than approximately 0.90. In all cases, do not exceed angles greater than 30 degrees from perpendicular
>> the hot spot should full the sensor spot size, ie 1" diameter at 12" distance.
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Re: Help with basking rock temp

Postby bryan » Fri May 24, 2019 10:35 am

I took the stone out of my encloure and immediately measured its temperature from 12 inches away, but the readings are still the same. I’d just be more comfortable if the temperatures were lower, since on a hot day like today with my air conditioning running, the rock is heating up in the center to about 114. Do you think a dimmer switch would do the job? I attached pictures of the dimmer I was looking into getting, as well as the bulb I’m currently using...thanks!!

DC8D9AC9-C088-483B-AF27-FF6869DCEEB9.jpeg


99856150-25E4-463D-BB3A-FCCED135F694.jpeg
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Re: Help with basking rock temp

Postby kingofnobbys » Fri May 24, 2019 11:54 am

I know people who keep skinks and dragons in very hot areas of Australia , who's homes are NOT airconditioned (except in some instances when they are home) .

What they do if the ambient is going to be in the high 30s degC (up in 90s F) is they simply unplug their basking globe from the powerboard and just keep the UV tube running as per normal on a timer. This eliminates the need to set up a dimming thermostat and ensures the lizards don't get cooked if it gets very warm in the house .

So really I'd suggest keeping everything as simple as possible , hot weather ==> basking globe turned off all day.

If you are going to opt for a dimmer , I'd make sure it's one that is controlled via a remote thermometer probe.
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Re: Help with basking rock temp

Postby mb606587 » Fri May 24, 2019 9:13 pm

114 degrees on the basking surface will not cook your skink, especially with the other temps you listed. I believe we as a community underestimate the temperatures our skinks prefer to bask on simply because so many people are quick to rely on and regurgitate the same numbers that keepers have used for decades. In Australia, these skinks are commonly found basking on roadways that oftentimes reach surface temperatures (not ambient air) in excess of 150 degrees Fahrenheit. Being that you keep your skink in a climate controlled house, I would not recommend switching off your basking lights on 90+ degree days. You'd be doing that quite a bit in New Jersey in the dog days of summer. Now obviously if he was in a hot garage that'd be a different story. I will try to get pictures up of my temp gun readings tomorrow morning when the lights turn on but my basking stones are usually kept at a minimum of 115 degrees, usually closer to 135ish. It's important to understand the difference between ambient air temperature and surface temperature. Many surfaces our skinks utilize to bask on both in captivity and in their natural habitat (slate, asphalt, concrete) will retain heat very well and register temperatures much higher than the actual air temperatures that our digital thermometers are reading.
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Re: Help with basking rock temp

Postby mb606587 » Sat May 25, 2019 8:00 am

Temperature readings taken this morning for the 3 of my skinks that were awake. If you can't see the readings because of my phone quality pictures they are 116, 139, and 126 degrees Fahrenheit. These skinks are frequent baskers. The first two Meraukes which are on the hotter rocks spend almost the entire day under the light and aren't even bothered by my hand coming over top of them.

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