Trouble setting up dubia enclosure

[Mattrg]

I'm planning on ordering some dubia roaches and I'm trying to get their place set up. The thermometer I have has read around 73 degrees and 42% humidity since I turned it on and put it in the enclosure a few hours ago. It's an all living things brand digital thermometer/hygrometer and my setup is a Rubbermaid tote roughly estimated at 1.5 ft l x 1 ft w x 1.5 ft h with egg cartons inside and a reptitherm Under tank heater meant for a 10-20 gallon terrarium strapped to one of the sides. Is my thermometer busted? Is my enclosure so big that the temperature wouldn't change more then a degree or 2? Do I just need to wait longer for it to heat up? Please any help would be great.

 

[Soulwind]

Set the probe on the hot spot and measure that for awhile.

Your air temps aren't going to go up tremendously. They will rise
a bit the longer the bin stays closed up (unless the vent area is too big),
but you won't get air temps up into the 90's.

Nor do you really need it. As long as the air temps are high 70's to mid 80's,
and there's a good hot spot for them to accumulate around they'll be fine.
They'll move to and away from the hot spot as needed.

You might try putting the UTH on the bottom instead of the side, or setting
the whole bin on a human heating pad (raised up on a wire shelf, so there's
some air circulation under/around the pad) to get some of the hot spot down towards the ground, then the whole colony can move up and down the egg
crates to get to the best temp level.

Plus, heat rises.

 

[Mattrg]

Ok I put the heater under the enclosure, layed both probes on the heated spot, and set 4 old ps2 game cases under each corner to prop it up. I let it sit like that for four hours and the temp went up to 83 which I think should be fine but the humidity dropped down to 23%.

 

[Mattrg]

One more message just to let you all know my problem is pretty much resolved and to thank you for the advice. Took another air temp/hydration measurement and its back to mid 70's and about 42% humidity guess the hygrometer probe isnt as accurate closer to the heat source or something. I'm assuming once I add the roaches and water pellets both will rise slightly which should be fine since I only need them to breed enough to feed one bearded dragon and a tarantula.