Temperature and Humidity Data Logger UK: The Complete Guide
TL;DR: A temperature and humidity data logger is a small device that records both readings at set intervals, so you can see the whole story rather than a single moment. It is not a thermostat — it watches and remembers instead of controlling. This guide explains how a logger records, how to read a log, what its accuracy figures really mean, and uses a reptile incubator as a running example of why watching both temperature and humidity over time actually matters.
Wall gauges and thermostat displays tell you what is happening right now. They forget everything the moment you look away — which is no help when the problem happens overnight or while you are at work. A temperature and humidity data logger fills that gap: it samples on a schedule, stores thousands of readings, and lets you replay exactly what the environment did.
What a data logger is (and is not)
A logger measures, timestamps and stores. That is the whole job. Crucially, it does not control anything — it will not switch a heater on or hold a set point. That is the thermostat's role. The two work best together: the thermostat runs the environment, and an independent logger keeps an honest, separate record of what actually happened, so you are not relying on the same box that is doing the controlling to also mark its own homework.
How it records
- Sampling interval: how often it takes a reading — every 15 minutes as a common default, adjustable for longer or finer records.
- Memory: how many readings it can hold before you download. A capacity of 32,000 readings covers roughly 11 months at 15-minute intervals, or a shorter window at faster sampling.
- Download: a USB logger writes its history to a PDF (and to free software if you want charts) when you plug it in. There is no cloud account and nothing to subscribe to.
How to read a log
Open the report and look past the average. The numbers that matter are the minimum and maximum, and any excursions outside the band you set. A tidy average can hide a nasty overnight spike; the point of logging is to expose exactly that. Set high and low alarm thresholds so the report flags when a limit was crossed, and check the shape of the curve, not just the endpoints.
What accuracy actually means
Two numbers describe a dual logger, and they are not equal. Temperature is usually the tighter figure — around ±0.5°C for a good unit in its core range. Humidity is inherently harder to measure, so a typical figure is nearer ±3%RH. That is normal and honest; be sceptical of any humidity sensor claiming temperature-like precision. If you need to trust the RH figure, verify it against a reference — see our guide on how to calibrate humidity sensors.
Running example: watching a reptile incubator
Few hobbies show the value of dual logging better than incubating eggs. Many gecko keepers care about temperature to the degree because sex is temperature-dependent: incubation is often held somewhere between roughly 26 and 33°C depending on species and the ratio you want, with sustained highs above about 33–34°C risking the clutch. Humidity typically sits high, often around 70–90%, to stop eggs dehydrating. Always check a current care sheet for your species — but the theme is constant: both readings matter, and small drifts count.
A thermostat holds the set point, but it does not tell you what happened at 3am or while you were at work during a 60-day incubation. An independent logger does. Because the Elitech RC-51H records temperature and humidity together, is rated IP67 for the damp inside an incubator, and stores the whole run, you can plug it in after hatching and replay the full curve — catching the thermostat wobble you would otherwise never have seen. It is a second, honest data source, not a replacement for the controller.
Where the Elitech RC-51H fits
As an all-round dual logger it is a sensible default: temperature and humidity in one IP67 waterproof pen-style body, ±0.5°C and about ±3%RH accuracy, 32,000 readings, automatic PDF reports with no software required, a replaceable ER14250 battery giving roughly two years of use, and a factory calibration certificate in the box. It carries a 12-month warranty with UK support, free next-day delivery and 30-day returns, at £52.14.
The one-line summary: a logger watches and remembers both temperature and humidity; your thermostat controls. Use both.
Related reading
Shopping to buy? See the USB temperature logger buyer's guide and best temperature data loggers for food businesses. Keeping a unit healthy is covered in data logger maintenance.
Frequently Asked Questions
What is a temperature and humidity data logger?
It is a small device that measures and stores both temperature and relative humidity at set intervals, then lets you download a time-stamped record. It shows the whole history rather than only the current reading.
Is a data logger the same as a thermostat or incubator controller?
No. A thermostat controls the environment to a set point; a logger only measures and records. They complement each other, with the logger giving an independent record of what the controller actually delivered.
What temperature and humidity should a reptile incubator hold?
It varies by species, but incubation often runs somewhere between about 26 and 33C with humidity around 70 to 90 percent. Sustained temperatures above roughly 33 to 34C can be dangerous, so always follow a current care sheet and monitor with a logger.
How do I check my incubator while I am at work?
Leave a data logger running inside it. You will not get a live alert from a USB unit, but you can plug it in later and replay the full temperature and humidity curve to see any drift you missed.