One thermometer or two?

I have a temperature gun which I use obsessively and a probed thermometer that I don't really trust, so I'm getting a new better one. Here's my question, apologies if it's stupid. I followed the "how to set up a 20 gallon long with pictures" guide and I admit, and I'm sorry, that I didn't use the aluminum foil part, but I trust my hygrometer well enough and humidity is on point. (I mist the tank, have a waterfall and obviously fill the water dish daily).
The question is... why the one thermometer, and why is the probe centered over the UTH? Wouldn't that only measure the hot side? Again, my therm is wildly inaccurate compared to my very nice heat gun so I guess I can't even tell for sure. Should there be two thermometers, one probe on the warm side and one one the cooler side? I for some reason can't wrap my head around one thermometer for two different temperatures. Again I apologize very much if this is a stupid question. Again, I'm getting a better thermometer delivered in two days but I wonder if I actually need two.

He of course has a thermostat for his UTH.

I use acurite 00891. I put probe on hot side and run the wire under substrate to cool side and set unit there and from the one screen it gives me hot temp, cool temp, and humidity. They are very accurate and give me the same readings as me Herpstat and VE thermostats.

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This one? http://www.walmart.com/ip/Acu-Rite-I...r-00891/896347


i suppose what I don't get is that it only shows one temperature but there are two sides with TWO temps to measure. feel very stupid/embarrassed right now so you know, perhaps I will just get that one, do as you say and then use a temp gun because I clearly cannot wrap my stupid head around this.

i have 2 of the accurites that i ordered online, i have one on the hot side under the substrate and 1 on the cool side that is barely just covered by substrate, then i get the humidity level on both sides of the tank, which is within 3-4 percent of each other, of course it is a 40 breeder instead of the 20 long..

here is the link to the amazon place where i bought mine,

https://www.amazon.com/Instruments-A...ter+with+Humid

Quote:

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Originally Posted by m1lkhoney

This one? http://www.walmart.com/ip/Acu-Rite-I...r-00891/896347


i suppose what I don't get is that it only shows one temperature but there are two sides with TWO temps to measure. feel very stupid/embarrassed right now so you know, perhaps I will just get that one, do as you say and then use a temp gun because I clearly cannot wrap my stupid head around this.

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Yes the acurite 00891, the thermometer shows the probe temp and the temp of wherever you set the whole unit so if you set the unit on the cool side it will show the cool temp on the screen but will also show the temp of where you have the probe which would be the hot temp, plus it shows humidity also wherever the unit is set. All your temps plus humidity for $12.

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Oh. OHHHHH. I get it now.

THANK YOU.