Damp towel. Cover 80-90% of the screen with a damp towel, tin foil, or plexiglass. Use a larger water dish and move it to the hot side of the tank. Wider water dish = Greater evaporation = greater humidity.
You can also use moisture retaining substrates like coco just or cypress mulch.
Probe in the enclosure in the hottest spot(like on the glass, over the uth and under the substrate. Or have it over the hot spot surface to measure surface heat from the lamp)
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