## Common ground
All options refer to devices that record data over time, typically for monitoring environmental or operational conditions.
## Options at a glance
**8471.90 – Combined computer**
- **Defining trait:** Functions as a full data processing machine (computer) with integrated logging capability.
- **Typical examples:** Industrial PC with built-in data logging software.
- **Best fit when:** The device is primarily a computer used for logging, not just a standalone logger.
**8517.62 – Mobile communication & data acquisition**
- **Defining trait:** Designed for wireless data transmission (e.g., cellular, Bluetooth) in addition to logging.
- **Typical examples:** Remote sensor node sending data via 4G.
- **Best fit when:** Real-time remote monitoring with network connectivity.
**8523.51 – SD card or solid-state storage**
- **Defining trait:** Uses removable or embedded flash memory as the primary storage medium.
- **Typical examples:** USB stick-style logger, SD card-based sensor recorder.
- **Best fit when:** The device relies on standard flash storage and lacks built-in processing.
**8537.10 – Programmable logic controller (PLC)**
- **Defining trait:** Designed for industrial automation with programmable control logic.
- **Typical examples:** Factory machine controller logging operational data.
- **Best fit when:** The device controls machinery and logs data as part of automation.
**9025.19 – Temperature-only logger**
- **Defining trait:** Specialized solely for temperature data capture.
- **Typical examples:** Cold chain monitoring device in shipping.
- **Best fit when:** Only temperature is measured, no other parameters.
**9025.80 – Temp & humidity logger**
- **Defining trait:** Simultaneously records both temperature and humidity.
- **Typical examples:** Environmental monitoring in museums or warehouses.
- **Best fit when:** Dual environmental parameter logging is required.
**9025.90 – Part of thermometer/hygrometer system**
- **Defining trait:** Not a standalone logger; part of a larger instrument system.
- **Typical examples:** A digital thermometer with optional data logging mode.
- **Best fit when:** The device is primarily a measuring tool, logging is secondary.
**9027.10 – Gas monitoring systems**
- **Defining trait:** Designed to detect and record gas concentrations (e.g., CO₂, methane).
- **Typical examples:** Indoor air quality monitor with data storage.
- **Best fit when:** The primary function is gas detection and logging.
**9031.80 – Measuring/checking instrument**
- **Defining trait:** Used as a precision measuring or verification tool with logging.
- **Typical examples:** Calibration device that logs readings over time.
- **Best fit when:** The device is used for measurement accuracy and compliance.
## Key differences
| Option | Primary Function | Storage Type | Connectivity | Specialization |
|-------|------------------|--------------|--------------|----------------|
| 8471.90 | Computer + logging | Varies | Often built-in | General-purpose computing |
| 8517.62 | Wireless data transmission | Varies | Cellular/Bluetooth | Remote, networked logging |
| 8523.51 | Flash-based storage | Flash only | Limited | Simple, low-cost logging |
| 8537.10 | Industrial control | Varies | Varies | Automation-focused |
| 9025.19 | Temperature-only | Varies | Varies | Single-parameter focus |
| 9025.80 | Temp & humidity | Varies | Varies | Dual environmental logging |
| 9025.90 | Part of instrument | Varies | Varies | Secondary logging function |
| 9027.10 | Gas detection | Varies | Varies | Gas-specific monitoring |
| 9031.80 | Precision measurement | Varies | Varies | Calibration/verification use |
## How to choose
- Does it primarily act as a computer? → 8471.90
- Does it transmit data wirelessly in real time? → 8517.62
- Is it based on an SD card or flash memory only? → 8523.51
- Is it used to control industrial processes? → 8537.10
- Does it record only temperature? → 9025.19
- Does it record both temperature and humidity? → 9025.80
- Is logging just a feature of a thermometer/hygrometer? → 9025.90
- Is it designed to detect gases like CO₂ or methane? → 9027.10
- Is it used for calibration or precision measurement? → 9031.80
## Overlaps & pitfalls
- A device that logs temperature and humidity may fit both 9025.80 and 9031.80 if used in calibration.
- A mobile data logger (8517.62) might also be a temperature logger (9025.19).
- **Priority rule:** Choose based on the device’s MAIN function—e.g., if it's for gas detection, use 9027.10; if it's a general-purpose computer, use 8471.90