Short answer: choose a contact sensor or data logger when you need a documented temperature record over time, and a thermal imaging camera when you need to see surface temperature differences across an area; then match range, accuracy, logging interval, alarms and enclosure rating to the job.
How do temperature instruments measure heat?
Contact instruments put a sensor in thermal contact with the thing being measured. Thermistors change resistance strongly with temperature and suit the everyday range used in food and storage. Thermocouples generate a small voltage at a junction of two different metals and cover very wide ranges. Platinum resistance sensors are stable and used where higher accuracy is needed.
A data logger adds a clock and memory, recording readings at a set interval so you can prove what happened while nobody was watching. Many also record relative humidity using a capacitive sensor.
Thermal imaging cameras are non-contact. Every surface emits infrared radiation depending on its temperature and its emissivity, a value between 0 and 1 describing how efficiently it radiates. The camera's detector converts that radiation into an image in which each pixel carries a temperature estimate.
Which type is right for my application?
| Instrument | Measures | Best for | Limitation |
|---|---|---|---|
| Probe thermometer | Core or liquid temperature, instant | Food checks, liquids | No record unless written down |
| USB / single-use data logger | Temperature (and humidity) over time | Cold-chain shipments, storage | Download needed to view data |
| Wireless / app logger | Live readings with alerts | Fridges, server rooms, greenhouses | Depends on signal and app |
| Hygrometer | Relative humidity and temperature | Storage, damp monitoring, instruments | Humidity sensors drift over time |
| Infrared spot thermometer | Surface temperature at one spot | Quick surface checks | Sensitive to emissivity and distance |
| Thermal imaging camera | Surface temperature map | Electrical hot spots, heat loss, mechanical wear | Reads surfaces, not air or internal core |
What specifications should I compare?
Range and accuracy. Check accuracy across the range you will actually use, not just at one point. Freezers, fridges and ambient storage have very different requirements.
Logging interval and memory. Shorter intervals catch brief excursions but fill memory faster. Calculate how long the logger will run between downloads.
Alarms. High and low thresholds, with visual, audible or app alerts, turn a passive record into an early warning.
Reports. For audits, a logger that produces a fixed report such as a PDF is easier to file than raw data.
Enclosure. Loggers in cold rooms, wash-down areas or outdoors need a suitable IP rating under IEC 60529, and probes need to suit the media they touch.
Thermal camera resolution and sensitivity. Detector resolution sets how much detail you see and how small a target can be measured at a distance. Thermal sensitivity, often quoted as NETD, describes the smallest temperature difference the camera can distinguish. Adjustable emissivity is essential for meaningful temperature figures.
Traceable calibration. If records support compliance, choose instruments that can be calibrated against reference standards; UKAS accredits calibration laboratories in the UK.
How are they used in the UK?
Food businesses in England operate under the Food Safety and Hygiene (England) Regulations 2013, which include temperature control requirements for chilled food, and the Food Standards Agency publishes guidance on chilling. Loggers and probe thermometers are the usual way businesses check and record that equipment is working. Equivalent legislation applies in Wales, Scotland and Northern Ireland.
Other common uses include pharmacy and vaccine fridges, wine and musical instrument storage, greenhouses, warehouse mapping, and transport of temperature-sensitive goods. Thermal cameras are widely used to find missing insulation, cold bridges and air leaks in homes, to spot overheating connections in electrical panels, and to check bearings and motors.
What mistakes should I avoid?
- Placing a logger by the door or in the evaporator airflow, so it records air spikes rather than product temperature.
- Measuring shiny metal with a thermal camera without adjusting emissivity, which can produce readings far from reality.
- Treating a thermal image as an air temperature reading.
- Never checking accuracy. Compare against a reference periodically.
- Choosing a logging interval that runs out of memory before the trip or audit period ends.
- Thermal surveys on warm days. Heat-loss imaging works best with a large indoor–outdoor temperature difference.
Frequently asked questions
What is the difference between a thermometer and a data logger?
A thermometer shows the temperature now. A data logger records readings automatically at intervals, so you can review conditions over hours, days or a whole journey.
Can a thermal camera see through walls?
No. It shows the surface temperature of the wall. Hidden pipes, studs or missing insulation become visible only because they change the surface temperature.
What is emissivity and why does it matter?
Emissivity is how efficiently a surface radiates infrared energy. Matt, dark surfaces are high; polished metals are low. Setting the wrong value makes temperature readings inaccurate.
Do I need a calibration certificate for my food fridge logger?
Requirements depend on your food safety management system and auditor. Many businesses check thermometers regularly against a reference; a certificate from an accredited laboratory gives formal traceability.
How often should a humidity sensor be checked?
Humidity sensors drift with age and exposure to contaminants. Check them against a reference periodically, more often in harsh environments.
What should I check before ordering?
Before you order any temperature instrument, write down the measurements or tasks it must handle, the range and accuracy you need, where it will be used and who will use it. Compare those notes with each product's specification sheet rather than its headline features, and keep the manual and any certificates with the instrument once it arrives.
Shop temperature and thermal instruments
Browse data loggers, wireless hygrometers and thermal imaging cameras in our Thermal & Temperature collection.
