Uneven Temperature Distribution- Equipment Accuracy

[SnakeCharm]

Hey everyone! Quick question....

Equipment

- 30 Gallon glass tank
- 30-40 Gallon ZooMed UTH
- Vivarium Electronics VE-200 Thermostat
- Fluker's Combo Thermometer/Hygrometer for monitoring ambient temperature set on cool side
- ZooMed Reptitemp digital infrared thermometer
- Aspen substrate with Coconut husk strewn in here and there
- Corner ziggurat hide for basking
- Fake leaves and a small hollow wood log for temporary "cool side" hide (I'm actually in the process of receiving his permanent "Temple of Doom" in the mail soon )

Issue

The VE-200 seems to be a decent product. I layed the probe directly above the UTH inside the tank and everything seems in order. As such, the numbers on the VE-200 would be reading the temperature on the glass only, right?

If I put .5"-.74" of substrate on top of the probe, the temp on top of the substrate would naturally be lower than what I set at the thermostat, correct? (eg., Thermostat set to 100. Probe reads 100. Glass is 100. Substrate is 95.)

My issue is that the infrared thermometer (Zoo Med's Reptitemp....is this even a good product? I have doubts.) is giving me readings of 89, 87, 84, 97, etc. when I go to verify the temp on the substrate where the snake will actually lay. This makes sense in a way, I suppose, due to uneven heat penetration of the substrate, but the inaccuracy and difference in readings between the infrared thermometer and the thermostat is a significant weak link and everything then falls apart because I am not confident in the temperature of the basking area. Is it too hot when I set it to 100? Is it too cold when I set it to 95? How much buffer is needed to account for heat absorption and penetration through the substrate? Furthermore, I know there is always the danger of the snake burrowing until it touches the glass and burns itself.

If there is any insight on this matter, I'd totally appreciate it...

Thanks everyone!

P.S. First time post. I've been reading quite a few threads in the forum and there is a ton of knowledge here. Awesome community and I'm glad to be a part of it.

[anicatgirl]

I actually am curious about this too, because my infrared does the same thing, and my Hygrotherm sensor reads different too... I fear it is confusing snake's eating habits. Anyone got a clue for us?

[SnakeCharm]

What kind of infrared thermometer do you have?

I am almost sure this is the problem- the digital infrared thermometer- and in my case, it is the ZooMed ReptiTemp. It had good reviews on Amazon, so I am really surprised at what I suspect is poor quality. I may just go boil a pot of water to get a known temp and compare. Aside from that, I will hold off on judging the VE-200 as being inaccurate, although I am replacing it with the HerpStat 2 anyway .

[KMG]

First the tstat probe does not go INSIDE the cage. It needs to be OUTSIDE between the uth and the bottom of the cage. If you already stuck the uth on the cage bottom you can also secure the probe under the uth. It should be placed in the middle and foil tape is a great choice to do so. Just tape the wire directly behind the probe and no the actual probe itself.

Next the amount of substrate over the uth should be 1/4 inch at most. Over my uth in the hides you can see the glass. You want the glass to be the hottest place the snake can reach and do not want to thick of a layer of substrate to block the heat. Doing this will make you raise the tstat temp higher and the snake can then burrow or push the substrate aside and get to the glass which will then be way to hot. I have about a two inch layer of substrate in the rest of the cage but the uth area is extremely thin.

As for the random temps it is going to be a mixture of the substrate and the way a uth is made. The uth pad has a heated wire that is zig zagged through the two layers of plastic cover. This zig zag pattern creates a gap between each loop and will cause a bit of uneven temps when measured going across the pad. As long as the numbers are somewhat close and within the desired range you are good. Bending and/or creasing the uth can also break the heating elements inside and cause dead spots and uneven temps.

[SnakeCharm]

Thank you, KMG.

I actually saw that here....
http://ball-pythons.net/forums/showthread.php?201740-How-to-Setup-a-Glass-Tank-%2820-long%29-With-Pictures!

..But I just don't understand it all the way...

In SerpentMerchant's thread, as I look at it again, he says pretty much what you just said. Place probe under (outside) tank, place thermometer probe inside the tank.

In a way, would it be inaccurate to say that it really doesn't matter what temperature the UTH is? It seems that what's important is the temperature he actually feels on the glass, so that's where you make the adjustments. So why not just place the probe from the thermostat inside? I feel that there may be something I am missing...

As far as the thermometer, any thoughts on the infrared vs. a probe as far as accuracy?

Also, you mentioned that if I had stuck the UTH pad to the tank already...I did stick it, and then I unstuck it, moved it and stuck it back. I understand the "stickiness" will go away at some point, but I am willing to give it another reattachment to fix the probe where it needs to go. Do you think it would be a problem to move it at this point?

I know I'm asking lots of questions, but please bear with me

I really appreciate your comment about the thickness of the substrate. I didn't know if it was okay for the snake to directly lay on the glass.

Thank you for the explanation of the UTH construction, as well. From that, I can see how the readings make sense.

[KMG]

In a way, would it be inaccurate to say that it really doesn't matter what temperature the UTH is? It seems that what's important is the temperature he actually feels on the glass, so that's where you make the adjustments. So why not just place the probe from the thermostat inside? I feel that there may be something I am missing...

You do not want to place the probe inside the cage because the snake could move it, pee on it, flip its water and flood the tank, etc. If these things were to happen and the probe was inside the cage it would tell the tstat that the uth is cold and needs to be warmer. This will ramp up the uth and could overheat and burn the snake. This is especially a concern if the snake was to move the probe to the side and then lay on the hotspot. The snake will most certainly be burned. Also never use tape inside the tank. It can make a mess of your snakes scales.

As far as the thermometer, any thoughts on the infrared vs. a probe as far as accuracy?

Every thermometer has a margin of error as does the tstat probe. This margin should be on the device itself or on the package. Some thermometers can be a few degrees up or down so that paired with the uth no actually heating 100% even will give you strange readings sometimes. As long as they are close and within range you should be good.

Also, you mentioned that if I had stuck the UTH pad to the tank already...I did stick it, and then I unstuck it, moved it and stuck it back. I understand the "stickiness" will go away at some point, but I am willing to give it another reattachment to fix the probe where it needs to go. Do you think it would be a problem to move it at this point?

Just do it very carefully. You could also cover the sticky part with foil and then just tape the uth in place on the bottom of the cage. This allows you to easily remove the uth so you can clean the tank or just reposition the uth.


Thank you for the explanation of the UTH construction, as well. From that, I can see how the readings make sense.

They are not all made that way and some are made more like heat tape and are more uniform. The one you have is fine though.

[SnakeCharm]

Wow! There are so many things I didn't consider. Thank you for your time in answering my questions in detail.

I will get into fixing this first thing in the morning!

[KMG]

No problem. Im glad I could help.

[anicatgirl]

OK not to but since we are kinda dealing with the same stuff I hope it's ok...... My sensor is inside my warm hide against the glass cause it is a Hygrotherm and it also regulates humidity, for which it needs be inside. Maybe not the best plan in retrospect...?

[Eric Alan]

Maybe not the best plan in retrospect...?

Correct.