A data logger is an electronic instrument that automatically records physical measurements — most commonly temperature, humidity, pressure or voltage — at regular intervals and stores the data for later retrieval, analysis and documentation. Data loggers are used wherever continuous monitoring, trend analysis or regulatory documentation of an environmental or physical parameter is required. In Singapore, data loggers are found in pharmaceutical cold rooms, food storage facilities, server rooms, shipping containers, laboratory ovens, industrial processes, building HVAC systems and field measurement campaigns.
Unitest Instruments supplies data loggers from Rotronic and Comark, calibrates loggers through our SAC-SINGLAS accredited laboratory, and offers loggers for hire through our instrument rental service.
Why Use a Data Logger Instead of a Handheld Instrument?
A handheld thermometer or gauge tells you the measurement at the moment you check it. A data logger tells you the complete history — every measurement, at defined intervals, over the entire monitoring period. This distinction is critical in several situations:
- Unattended monitoring: Cold rooms, server rooms and warehouses cannot be manually checked every few minutes around the clock. A logger provides a continuous record even overnight, on weekends and through holidays.
- Compliance documentation: SFA, HSA, MOH and GMP regulations require documented temperature records that can be produced during audit. A logger generates this automatically; manual logs require disciplined staff and are prone to transcription errors.
- Detecting intermittent events: A brief temperature excursion caused by a compressor cycling off or a door left open may resolve before a manual check is performed. A logger captures the event with its exact timing and magnitude.
- Trend analysis: Logger data enables trending — identifying gradual drift in refrigerator performance, seasonal patterns in ambient humidity, or the effect of changes in room occupancy on server room temperature — that is impossible with spot checks.
- Shipment monitoring: For cold-chain logistics, loggers travel with the shipment, recording temperature throughout the journey. The data can be downloaded on delivery to confirm that the product was not exposed to out-of-specification conditions in transit.
Types of Data Loggers
Standalone USB Data Loggers
Small, battery-powered loggers with onboard memory and USB connectivity. They are programmed (start time, sampling interval, alarm thresholds) via a PC before deployment, then operate autonomously. At the end of the monitoring period, they are connected to a PC via USB and the data is downloaded for analysis. They are low-cost, self-contained and simple to use. Common applications: in-transit temperature monitoring for pharmaceutical and food shipments, equipment qualification studies, laboratory chamber monitoring.
Wireless Data Loggers
Wireless loggers transmit data in real time (or at intervals) via Wi-Fi, Bluetooth, LoRa or cellular networks to a central platform. They enable remote monitoring without physical data retrieval — alarms can be sent immediately to responsible staff by SMS or email when a threshold is exceeded. Common applications: pharmaceutical cold rooms, server rooms, HACCP monitoring in food businesses, building management. Rotronic wireless loggers, available from Unitest Instruments, support multiple wireless protocols and integrate with facility management systems.
Multi-Channel Data Loggers
Multi-channel loggers accept inputs from multiple sensors simultaneously — for example, 8 thermocouple inputs for temperature mapping of a furnace, or 4 temperature + 2 humidity + 2 pressure channels for a complex HVAC system. They are used in applications requiring simultaneous measurement at multiple points, such as temperature distribution studies, cleanroom qualification and industrial process monitoring.
Paperless Chart Recorders
Paperless chart recorders are industrial-grade logging systems designed for continuous, long-term monitoring in process environments. They display real-time data on a colour touchscreen, log to internal memory and SD card, and support industry-standard communications (Modbus, PROFIBUS, Ethernet). They replace traditional paper chart recorders in industrial applications where data integrity, tamper evidence and long storage life are critical.
Handheld Data Loggers with Display
Some loggers include a real-time display showing current readings alongside logging function. These instruments are used where the technician needs to read and record data simultaneously — HVAC commissioning, equipment testing, environmental surveys. They bridge the gap between a handheld instrument and a pure data logger.
Key Parameters Logged by Data Loggers
| Parameter | Typical Sensors | Common Applications |
|---|---|---|
| Temperature | PT100 RTD, thermocouple, thermistor | Cold chain, HVAC, pharmaceutical, food, server rooms |
| Relative humidity | Capacitive thin-film sensor | Pharmaceutical, cleanroom, HVAC, server rooms, archiving |
| Differential pressure | Piezoresistive, capacitive | Cleanroom, ductwork, filter monitoring |
| Voltage / current | Input terminals | Power monitoring, battery testing, process control |
| CO2 | NDIR optical sensor | Office air quality, greenhouse, incubators |
| Dew point | Chilled mirror, capacitive | Compressed air, gas pipelines, cold stores |
Selection Criteria for Data Loggers
Choosing the right data logger requires matching the instrument to the application across several key criteria:
Measurement Range and Accuracy
Ensure the logger covers the full range expected in your application with adequate accuracy. For pharmaceutical cold chain (+2 °C to +8 °C), accuracy of ±0.5 °C is typically sufficient; for cleanroom temperature control (±0.5 °C setpoint), you may need ±0.1 °C. Humidity accuracy of ±2–3% RH is typical for most loggers; high-precision applications may require ±1% RH.
Sampling Interval
Shorter intervals capture more detail but fill memory faster and increase data volume. For cold-chain monitoring, 5–15 minute intervals are standard. For industrial process monitoring or event detection, 1-minute or shorter intervals may be needed. Ensure the logger's memory capacity at your chosen interval covers the full deployment period.
Connectivity and Data Download
Match the connectivity to your workflow. USB loggers require physical retrieval; wireless loggers allow remote access. For regulated environments, consider whether 21 CFR Part 11 audit-trail compliance is required. For integration with building management systems, Modbus or BACnet protocol support may be necessary.
Alarm Capability
Loggers used for compliance monitoring must be able to raise alarms when thresholds are exceeded. Local alarms (LED, buzzer) alert nearby staff; remote alarms (SMS, email, SNMP trap) alert staff who are not in the area. Alarm delay settings prevent nuisance alerts from brief, non-harmful excursions.
Battery Life and Power Supply
For field deployment or shipping applications, battery life must cover the full deployment period with margin. For fixed installations, mains-powered loggers with battery backup maintain monitoring through power interruptions — critical for pharmaceutical and food cold chain.
IP Rating and Environmental Robustness
For food production, cleanroom or outdoor applications, the logger housing must be rated for the environment. IP65 or IP67 ratings protect against ingress of dust and water. Food-safe materials (no crevices that harbour bacteria) are required in food processing environments.
Calibration of Data Loggers
All data loggers used for compliance monitoring must be calibrated at defined intervals with traceability to national standards. In Singapore, calibration by a SAC-SINGLAS accredited laboratory is required for data used in regulated applications (pharmaceutical, food safety, environmental monitoring).
Unitest Instruments' SAC-SINGLAS accredited laboratory (LA-2023-0845-C) calibrates temperature, humidity and pressure data loggers across the ranges used in Singapore's regulated industries. Our calibration certificates include all information required by HSA, SFA and international auditors — including the measurement uncertainty, the reference standards used and the traceability chain to national standards. Standard in-lab turnaround is 3–5 working days. View our calibration services or contact us for a quotation.
For periodic qualification studies or short-term monitoring requirements, our data logger rental service provides calibrated loggers ready to deploy, avoiding capital purchase for infrequent use cases.