Quick answer: A temperature and humidity data logger records conditions at set intervals so you can prove what happened in a warehouse, truck, cleanroom, greenhouse or drying job. Choose by accuracy (±2–3 % RH and ±0.3–0.5 °C for most uses), logging interval (5–15 minutes for storage; 1 minute for fast events), memory and battery life for the period you need, connectivity (USB download, Wi-Fi, cellular, LoRa or BLE gateway) and alarms. For regulated uses (pharmaceuticals, food), also check calibration certificates and data-integrity features such as audit trails.
Quick answer
- Accuracy: ±2–3 % RH, ±0.3–0.5 °C for most uses; calibrated with a certificate for audits.
- Interval: 5–15 minutes for storage, 1 minute for events.
- Networked loggers with alarms beat download-only loggers when problems must be caught early.
Specification checklist
| Specification | What to look for |
|---|---|
| RH accuracy and range | ±2–3 % RH over the range you need (including high humidity if relevant) |
| Temperature accuracy and range | ±0.3–0.5 °C; extended ranges for cold chain |
| Logging interval | Adjustable; fast enough to capture the events that matter |
| Memory | Enough for the full period at your interval |
| Battery | Life at your interval and connectivity setting |
| Connectivity | USB, Wi-Fi, cellular, LoRa or BLE to a gateway |
| Alarms | Local display, buzzer, email/SMS; with delays to avoid nuisance alarms |
| Probe | Internal or external; external probes for tight spaces or condensing areas |
| Calibration | Traceable certificate; recalibration interval |
| Software | Export, reports, audit trail, user access control |
Interval vs memory: quick sizing
Number of readings = days × 24 × 60 ÷ interval (minutes)
Example: 90 days at a 5-minute interval = 90 × 24 × 60 ÷ 5 = 25,920 readings per channel. Check the logger's memory against that.
Where to place loggers
- At the product or crop level, not at head height near the door.
- At the worst points: near doors, cold walls, top of racks, coldest corner.
- Away from heaters, lights, sun and dehumidifier or HVAC outlets.
- For a new site, use several temporary loggers to map conditions, then fix permanent points.
See industrial temperature and humidity monitoring and dew point sensor placement.
Data integrity for regulated records
In GMP environments, records must be attributable, legible, contemporaneous, original and accurate, with audit trails for changes. The US FDA's guidance on data integrity in drug manufacturing explains these expectations (FDA). Choose software that logs who changed what and when, and keep calibration records linked to each logger. NIST describes hygrometer calibration (NIST).
Using the data
- Find the cause of problems: line up humidity spikes with door openings, irrigation, shifts or equipment states.
- Check equipment: a dehumidifier that runs but humidity keeps rising points to a larger load, a fault or poor distribution.
- Prove conditions for customers, insurers or auditors.
If loggers show humidity regularly above your limit, see how to size a dehumidifier and our industrial dehumidifiers.
FAQ
Frequently asked questions
What is a temperature and humidity data logger?
A device that measures and records temperature and RH at set intervals for later review or live monitoring.
How often should a data logger record?
Every 5–15 minutes for most storage; every minute or faster for short events.
Do data loggers need calibration?
Yes, typically every 6–12 months for audited uses, with a traceable certificate.
Sources
- US FDA, Data integrity and compliance with drug CGMP: questions and answers.
- NIST, Hygrometers.
