An open table needs different measuring than a glass tank
A Russian tortoise, also called a Horsfield's tortoise, is usually kept in an open-topped table or pen, not a sealed vivarium, and that changes what your instruments must do. Warm air escapes upward, the basking lamp creates one intense hot spot on a flat stone or slate, and the far end stays close to room temperature, which is exactly the contrast this steppe species evolved to shuttle between. Air temperature in the middle tells you almost nothing. You need a way to measure the basking surface itself, the cool-end floor, and the humidity inside the sheltered hide where the tortoise sleeps and digests out of the dry room air.
The three readings that matter for this tortoise
First, the basking surface: an infrared temperature gun is the right tool, aimed at the stone directly under the lamp after it has warmed fully, because a probe left on that stone will be bulldozed aside by a determined tortoise within the day. Second, the cool end: a digital probe thermometer resting at floor level in the shaded end confirms the retreat is genuinely cooler and has not crept up in summer. Third, humidity: a small digital hygrometer placed inside or at the mouth of the humid hide, not out on the dry table, because Russian tortoises seek a moister microclimate in the hide even though the open enclosure as a whole should stay fairly dry, especially for adults.
Placement that survives a digging, pushing tortoise
Russian tortoises dig into corners, bulldoze ornaments, and climb surprisingly well, so treat every cable as temporary unless it is routed outside the pen walls. Keep the gun in your hand rather than mounted. Anchor the cool-end probe under the edge of a heavy hide or along the wall at substrate height, and recheck it after the tortoise's morning dig, which can bury a sensor under excavated soil and produce a falsely cool, stable reading. Position the hygrometer where kicked-up substrate will not coat its sensor, and wipe the sensor face during weekly cleaning, since a film of dust in a dry table steadily dulls humidity readings.
Reading a steppe pattern: hot spot, cool floor, damp hide
A healthy pattern for this species is contrast, not uniformity. The basking stone should be by far the hottest point the gun finds, the cool floor should be close to a comfortable room temperature, and the hide interior should read noticeably more humid than the open table. If the gun shows the whole table warming evenly on a hot day, the tortoise has lost its retreat and needs shade, ventilation, or a cooler room, not a weaker lamp alone. If the hide hygrometer reads no higher than the room, the hide substrate is too dry or the hide is too exposed to the lamp's drying heat. Juveniles, who desiccate faster than adults, make that hide reading especially important.
The morning lamp check as the anchor habit
Most Russian tortoise problems with temperature start with a lamp that failed, slipped on its clamp, or is aging and dimming, discovered days late because the tortoise simply ate less. Make the gun check part of the morning feed: lamp on, stone warming, greens down, gun reading taken while the tortoise approaches. That pairing of feeding and measuring is simple to keep consistent with KinsLe Care Teams holding the morning feed-and-check as one assigned duty for this tortoise, its completion timestamped so an unlit lamp never goes unnoticed until evening.