Where to put your probe
(and why it beats accuracy).
A ±0.2 °C sensor in the wrong place is less useful than a cheap one in the right place. Placement decides what your thermostat is actually controlling.
Put the probe where the temperature matters to the animal, not where it is convenient to run the cable. For belly heat, that means in contact with the surface the animal lies on, at the hottest point of the heated area. For a basking zone, it means at the basking surface itself. For ambient control, it means in open air, shaded, away from any heat source. The thermostat does not regulate the enclosure — it regulates the one point your probe is touching, and everywhere else is a consequence of that.
The thermostat only knows one point
This is the idea everything else follows from. A thermostat reads one temperature, compares it to one setpoint, and switches one output. It has no model of your enclosure, no idea where the animal is, and no way to know that the spot it is measuring is not the spot that matters.
Move the probe three centimetres and you have changed what the thermostat is controlling — without changing a single setting. That is why placement outranks sensor accuracy. An expensive probe measuring the wrong point reports a precise, trustworthy, irrelevant number.
Belly heat: mats, heat tape, cable
- In contact with the surface the animal lies on — the floor of the tub, the glass above the mat, the substrate surface over the heated area. Not inside the mat, not under it unless the manufacturer says so.
- At the hottest point, not the average. Heat tape and mats have hot spots, usually toward the centre of the element. Find it with an infrared thermometer before you tape anything down.
- Under whatever the animal will actually be under. A probe reading bare glass while the animal lies on 4 cm of aspen is reporting a temperature the animal will never experience.
- Secured. A taped probe that peels loose in a warm tub is a probe now measuring air, and the thermostat will happily drive the mat harder to compensate.
The failure this prevents
A probe sitting in air above a heat mat reads cooler than the mat surface. The thermostat sees a cool reading, adds power, and the surface the animal is actually lying on climbs well past the setpoint. The display says 32 °C the whole time — and it is telling the truth about the air. Thermal burns from belly heat are usually a placement problem rather than a thermostat problem.
Basking zones: bulbs and overhead elements
Overhead heat creates a steep gradient. The air 10 cm below a bulb and the surface of the rock directly beneath it can differ by a lot, and only one of them is what the animal lies on.
- On the basking surface — the branch, the rock, the platform — at the point directly under the heat source.
- Not dangling in mid-air below the lamp. That measures neither the surface nor the ambient, and it drifts with every air current.
- Shielded from direct radiant heat if you are controlling air temperature rather than surface temperature. A bare sensor in a beam reads the beam, not the room.
- Check with an infrared thermometer once it is running. Radiant heat is the hardest case to reason about and the easiest to measure.
Ambient and humidity
- Open air, mid-height, shaded. Away from the heat source, away from the glass, away from the door.
- Not on the cool-end floor. That is the coldest point in the enclosure and will read several degrees below the working ambient.
- Humidity sensors need airflow. Buried in substrate or tucked behind a hide, a humidity probe reports a microclimate nothing else in the enclosure shares — and it will be slow to respond to misting.
- Not in the misting cone. Direct spray saturates the sensor and gives you a reading that takes a long time to recover.
The mistakes worth naming
- Sharing one probe between two zones. The second zone regulates to a temperature that does not exist where it is heating.
- Placing for cable convenience. The shortest route is rarely the right point.
- Setting the target before confirming placement. Change the position and the same setpoint now means something different. Place first, then tune.
- Never checking it again. Animals move things. Substrate gets rearranged. A probe that was right in March may be sitting in open air by August.
- Trusting calibration to fix placement. An offset corrects a sensor that reads consistently wrong. It cannot correct a sensor measuring the wrong place, because the error changes with every power level and every ambient shift.
Verifying placement
Once the probe is where you want it, confirm the enclosure agrees:
- Let it stabilise. Give the enclosure time to settle after any change before judging anything.
- Walk the enclosure with an infrared thermometer. Basking surface, warm floor, cool floor, mid-air. Write the numbers down.
- Compare against what the thermostat reports. You are not looking for agreement — different points have different temperatures — you are looking to understand the relationship.
- Check the gradient is real. A thermostat holding one point perfectly while the whole enclosure sits at the same temperature means the animal has nowhere to thermoregulate.
- Re-check seasonally, and after any change to substrate, furniture or heat source.
Telling the controller where the probe sits
Here is the part most thermostats ignore entirely. If a probe is mounted on the heating element itself rather than on the surface the animal uses, the number it reports is systematically higher than the air or the basking surface — the element is always hotter than what it is heating. Set your target to the basking temperature you want and the enclosure lands below it, every time.
You can correct for this by hand, by working out the difference with an infrared thermometer and adjusting the setpoint until the surface lands where you want it. That is tedious, it has to be redone whenever anything changes, and it is the single most common reason a correctly configured thermostat produces a too-cool basking spot.
Why the Ectoscale 6 asks where your probe is
Before OphidianAI generates a climate profile, it asks one question about the second heating zone: is the probe surface-mounted on the heating element, or is it on the basking spot itself? On a surface mount it applies an offset, so the resulting air and basking temperatures still land on the target the species actually needs. On a basking-spot probe it applies none, because the probe is already measuring the thing you care about. The profile flags an estimated setpoint explicitly rather than quietly presenting a corrected guess as a measurement.
It is a small question, and it is the difference between a generated profile that is approximately right and one that is right for your enclosure. The reasoning behind every profile is written out in full before anything is applied, and nothing reaches a live enclosure without you approving it first.
Everything else on the unit follows the same principle: per-sensor calibration offsets against your own reference thermometer, so the controller matches the instrument you trust rather than asking you to trust it blind.
A profile that knows where your probe is
OphidianAI asks where the probe sits before it generates anything, and shows its reasoning before a single value reaches your enclosure.