To learn how to use a reptile hygrometer accurately, first identify which physical part senses humidity, position that sensor according to your exact model's manual, and check whether the screen is showing a live current reading or a stored minimum/maximum extreme. Writing down a percentage without recording where the probe sits, which display mode is active, and when memory was last cleared leaves the reading incomplete.
Start with your hygrometer's model code and instruction sheet. The three documented instruments below use different probe layouts—a single remote humidity sensor, a combined temperature-and-humidity sensor, and two separate probes—so their mounting rules and button sequences are not interchangeable.
Trace the sensor before mounting the display
| Documented model | Sensor arrangement | What to identify on your equipment |
|---|---|---|
| Exo Terra PT2477 | Remote humidity sensor | The humidity sensor and its cable, rather than the outer display housing |
| Exo Terra PT2470 | One combined temperature-and-humidity sensor | The single shared sensing probe location |
| Zoo Med TH-31 | Independent temperature and humidity probes | Which of the two probes measures humidity vs. temperature before placing them |
Write down the model code and label each probe in your enclosure notes before routing any cables.
Choose a location using the matching instructions
The September 2022 English manuals for the Exo Terra PT2477 and Exo Terra PT2470 advise checking that the sensor cable reaches your target spot before sticking or sliding the display unit into place. Both manuals describe mounting the display outside the terrarium using the supplied hook-and-loop fastener or sliding it into an Exo Terra Compact Top rail, while keeping the sensor away from direct heat lamps or UV bulbs.
| Model and arrangement | Its documented sensor placement |
|---|---|
| Exo Terra PT2477 (September 2022 manual) | For a single unit, place the sensor in a suitable central spot. When using multiple units, place one sensor in the driest zone and another in the most humid zone. |
| Exo Terra PT2470 (September 2022 manual) | For a single unit, place the combined sensor in a suitable central spot. When using multiple units, place one sensor in the warmest/driest zone and another in the coolest/most humid zone. |
Zoo Med's TH-31 Digital Combo Thermometer Humidity Gauge page places the main digital readout outside the enclosure in a dry spot and mounts its two independent probes inside with suction cups so temperature and humidity can be monitored in different zones. Crucially, Zoo Med's waterproof and submersion statements apply specifically to the temperature probe—never submerge the humidity probe in water. Its FAQ also warns to secure probe cables so reptiles cannot chew or tangle in the wire.
Keep a quick sketch of where each probe sits inside the vivarium alongside your model number.
Separate the current reading from minimum and maximum memory
For the Exo Terra PT2477 (humidity) and Exo Terra PT2470 (temperature and humidity), the September 2022 manuals specify this four-step MIN/MAX button sequence:
- Press once to show the stored maximum (MAX) reading.
- Press twice to show the stored minimum (MIN) reading.
- Press three times to return to the live current reading.
- Press and hold for 2 seconds to clear and reset the stored minimum and maximum memory.
Important boundary on MIN/MAX memory: Neither the PT2477 nor the PT2470 manual provides a clock or occurrence timestamp for when a stored minimum or maximum happened. A stored MAX or MIN figure only tells you the highest or lowest value reached since the last 2-second memory reset—so always log the exact time you cleared the memory alongside the time you read the display. Because the cited Zoo Med TH-31 page does not list this Exo Terra button sequence, do not apply PT2477/PT2470 button presses to the TH-31.
Finish with a usable reading record
Use the six-row log below right after checking or resetting your display so every reading stays paired with its probe position, display mode, and reset time:
| Record | Example of the information to supply yourself |
|---|---|
| Instrument and quantity | Your exact model (e.g., PT2477, PT2470, or TH-31) and whether the figure is humidity (% RH) or temperature |
| Sensor location & sketch note | Which specific probe is being read and its exact height/zone inside the enclosure (away from direct heat/misting jets) |
| Display state (mandatory) | Whether the screen shows Current, stored MAX (1 press on PT2477/PT2470), or stored MIN (2 presses on PT2477/PT2470) |
| Observation and memory reset time (mandatory) | The displayed reading, the clock time you read it, and the exact time you last held the button for 2 seconds to reset MIN/MAX memory (since extremes carry no internal timestamp) |
| Unresolved setup question | Any missing manual page, unidentified probe cable, or uncertain mounting spot to verify before relying on the number |
This log records how your instrument is positioned and read; species-specific humidity targets and laboratory calibration routines fall outside display operation and belong in your species care plan.
Browse Pawlivy's thermometers and hygrometers category to compare enclosure monitoring gear, and see our reptile tank cleaning guide to keep probes and displays out of harm's way during habitat cleaning.