What Is a Data Logger and How Does It Work?
A data logger is a small, battery-powered device that automatically samples one or more sensors at set intervals and stores timestamped readings, then makes them available via USB, Bluetooth, Wi-Fi or the cloud. Core parts are sensor(s), signal conditioning, ADC, microcontroller, memory, power and communications. In Australia, they’re used for vaccine cold chain (Strive for 5), HACCP food safety, labs, logistics and HVAC to create audit-ready records.
A data logger (also called a data recorder or DDL) is a portable instrument designed for unattended monitoring. It wakes up on a schedule, records, and sleeps to save battery. Unlike SCADA/DAQ systems (always-on, networked, operator-driven), loggers are stand-alone and optimised for long-term field use.
How a Data Logger Works
Signal path: Sensor, conditioning, ADC, microcontroller, timestamped memory, local/remote download.
Key settings: sampling interval, start/stop, alarm thresholds, units, logging mode (wrap/stop). Data access: USB/BLE apps for quick offloads; Wi-Fi/LTE/cloud for live dashboards and alerts.
Common Types
By Parameter
Temperature / Humidity / Temp-Humidity (fridges, rooms, transport)
Voltage/Current/Power (energy checks, PQ events)
CO₂/Pressure/Light (IAQ, packaging, photometrics)
Shock/Vibration (transport validation)
By Form Factor
USB “stick”: cheapest, plug-in downloads
Bluetooth: phone app, on-site checks
Cloud-connected: Wi-Fi/LTE, alerts & dashboards
Multi-channel bench/industrial: thermocouples/RTDs, mapping studies, wide ranges
When to Choose Which (quick picks)
Vaccine fridge: buffered temp probe + 5-min logging + alarms
Food coolroom: multiple TH loggers at warm spots for HACCP
Pharma warehouse: multi-point mapping then continuous monitoring
Core Specs to Compare
Accuracy vs resolution: pick accuracy aligned to your tolerance (e.g., vaccine work needs tight accuracy and verifiable calibration).
Sensor & range: thermistor/RTD (high accuracy), thermocouple (wide range); confirm probe interchangeability.
Sampling & memory: ensure interval suits the risk (5 to 15 min is common for fridges).
Power: replaceable vs rechargeable; battery life at chosen interval.
Ingress protection (IP) & operating temp: match environment.
Alarms: local buzzers/LEDs plus SMS/email for after-hours.
Calibration & certificates: request NATA-endorsed certificates when records must be SI-traceable for audits.
Australian Use Cases & Standards
Vaccines & healthcare (Strive for 5): keep +2 °C to +8 °C (aim +5 °C), use a data logger or automated monitoring, and download/review data to assess any breach. Victorian guidance specifies 5-minute intervals for vaccine fridges and weekly review of automated systems.
Food & beverage (HACCP): continuous logging provides evidence at CCPs. FSANZ notes ~4.7 million cases of foodborne illness/year in Australia, with ~47,900 hospitalisations and 38 deaths, underlining the value of reliable records.
Pharma logistics (GDP) & mapping: temperature mapping of storage areas and warehouses is expected under WHO Annex 9-aligned programs adopted in Australian practice; local guidance highlights mapping and ongoing monitoring to verify hot/cold zones before placing permanent sensors.
Getting Reliable Data (How-To)
Probe placement
Put probes at centre, corners, near doors/warm spots, and at multiple heights (warehouse).
Avoid direct contact with walls, coils, or fans; allow equilibration after moving sensors.
Configure
Sampling: start at 5 to 15 min for fridges; faster for unstable environments.
Alarms: set pre-alarm cushions (e.g., ±0.5 °C from limits) and escalation contacts.
Time sync: align to local time/AEDT; check daylight-saving rollover.
Verify
Quick ice-point/boiling-point checks where appropriate; schedule accredited calibration.
For new fridges/rooms, run a 24 to 72 h mapping with multiple loggers (empty and operational, seasonally if possible). World Health Organization
Maintenance & Calibration
Sensors drift with time, shock and environment. Regulated sites commonly use a risk-based 6 to 12 month cadence; lower-risk applications may extend farther with evidence. Choose NATA-accredited (ISO/IEC 17025) labs reporting uncertainty and traceability per NATA’s Metrological Traceability Policy this is what auditors recognise across Australia (via ILAC). NATA+
CISCAL note: Our NATA-accredited capability (Accreditation No. 411, Site 404) includes multi-channel thermocouple data recorders and digital temperature systems. See the CTA below.
Buyer’s Checklist
Accuracy Channels & sensor type, Logging interval & memory, Alarms & remote alerts, Battery life, Operating range & IP rating, Software/export formats, NATA-calibration support, Local service & turnaround.
Example Configurations
GP vaccine fridge
1x temp logger with buffered probe, 5-min sampling, daily min/max check, weekly review/download, and back-to-base alerts for deviations.
Food coolroom
2 to 4 TH loggers (door, centre, warm spot, return-air side), monthly reports for HACCP verification; investigate excursions with timestamped logs.
Pharma warehouse
Run mapping (utilizing multiple loggers at various heights and locations); identify hot/cold zones, then install permanent, monitored probes with alarms; remap after HVAC/layout changes, or as required seasonally.
Glossary
Accuracy: closeness to the true value (not the same as resolution).
Resolution: smallest display increment.
Sampling interval: time between measurements.
CMC: lab’s Calibration and Measurement Capability (uncertainty).
IP rating: ingress protection (dust/water).
Mapping: multi-point temperature study to characterise a space.
Validation: documented evidence the system consistently performs as intended.
GDP/GMP: Good Distribution/Manufacturing Practice.
NATA: National Association of Testing Authorities (ISO/IEC 17025 accreditation in AU).