What is the difference between a data logger and a GPS temperature tracker?
A temperature data logger is a small, self-powered recorder that travels with the goods and stores readings at a set interval. Its record is usually read after the trip, by USB, a PDF report or a phone app. It proves what the goods experienced, but on its own it cannot warn anyone during the journey.
A GPS temperature tracker is a sensor wired or paired to the vehicle's tracker. It sends readings with the vehicle's location while the trip is running, so the control room can see a rising temperature and call the driver before the load is lost. It belongs to the vehicle, not to the consignment, and it depends on vehicle power and mobile coverage.
When a data logger is the right tool
Choose a logger when the record has to stay with the shipment: pharma and vaccine consignments, goods that change vehicles or modes on the way, or customers who ask for a per-shipment temperature report on delivery. A logger placed inside the cartons measures closer to the product than a sensor fixed in the truck body.
Check the logger's calibration certificate, its logging interval, battery life for the longest trip, and how the data is read and stored at the destination. WHO's guidance on transport monitoring expects records to be kept and reviewed, not just collected.
When a live GPS temperature tracker is the right tool
Choose live tracking when you need to act during the trip: food and dairy routes with tight ranges, long hauls where a reefer unit failure could ruin the whole load, or fleets where the control room handles many vehicles at once. Alerts for high or low temperature, door opening and reefer power loss are what turn a reading into a decision.
Ask how readings are handled when the vehicle loses network. A good tracker stores readings and sends them when coverage returns, with each reading keeping the time it was measured, not the time it arrived. Without that, a gap in coverage looks like a gap in the cold chain.
Why many reefer fleets use both
The two answer different questions. The tracker answers "is this truck holding temperature right now, and where is it?" The logger answers "what did this consignment experience from loading to delivery?" A pharma distributor may need the logger's record for the customer and the tracker's alerts for its own control room.
If you use both, compare them after a few trips. A sensor in the return air of the reefer unit and a logger inside the load will not read the same, and knowing the usual difference stops false alarms.
Where the sensor sits matters more than the device
WHO's technical supplement on qualifying refrigerated road vehicles describes temperature mapping: measuring the load space to find the warmest and coldest spots. Air near the doors, the roof and the evaporator outlet behaves differently from air in the middle of the load.
Place the fixed tracker sensor where mapping shows the risk, keep it away from direct cold air from the evaporator, and record its position. When an excursion is reviewed, the first question is which sensor saw it and where it was.
Questions to ask before you buy
For a logger: accuracy and calibration certificate, interval, battery life, single-use or reusable, and how reports are shared. For a tracker: which sensors it accepts, alert settings, how offline readings are stored and sent, how long history is kept, and whether reports can be shared with customers.
SafarTrak trackers support 1-Wire temperature sensors, and the platform records each temperature reading with its own time alongside the vehicle's location. The cold chain page explains how alerts and reports work for reefer fleets.
Frequently asked questions
Is a data logger enough for a refrigerated truck?
It is enough to prove what a shipment experienced, but not to save it. A logger is usually read after the trip, so a reefer failure on the road is only discovered at delivery. Live tracking adds alerts during the trip.
Can a GPS tracker record temperature?
Yes, when a supported temperature sensor is connected to it. The tracker sends each reading with the vehicle's location and can raise alerts when the temperature goes outside a set range.
Where should the temperature sensor be placed in a reefer truck?
Where temperature mapping shows the highest risk, usually not directly in the cold air from the evaporator. Record the sensor position so readings can be interpreted during an excursion review.
What happens to temperature readings when there is no network?
A good tracker stores readings while offline and sends them later, each with the time it was measured. Ask the supplier to show this before you buy, because some devices send only the latest value.
Sources and further reading
Monitoring practice summarised from WHO technical supplements on temperature-controlled transport (TRS 961, Annex 9), checked on 14 November 2026. Product-specific accuracy, logging intervals and approvals vary; confirm them with the device maker and your customer's quality requirements.
BRING IT TO YOUR FLEET
Start with your vehicles.
Ask the right questions.
Share your vehicle mix, existing devices and required signals with the SafarTrak team.
See SafarTrak for cold chain logisticsDiscuss your deployment
