What Is a Temperature and Humidity Data Logger? Types and Selection Criteria
A temperature and humidity data logger measures the temperature and relative humidity where it is placed at set intervals and stores them with date and time.
A temperature and humidity data logger is a small battery-powered device that measures the temperature and relative humidity where it is placed at set intervals and stores them in memory with date and time. It is used to document conditions over days or weeks in warehouses, cold rooms, archives, pharmaceutical and food shipments, server rooms and inside panels. Unlike temperature and humidity meters, which are made for spot readings, it records on its own without interruption.
Types
| Type | How the data is read | Models in the catalog |
|---|---|---|
| USB logger | Plugged into a computer's USB port to read the record | UNI-T UT330B, UT330C |
| Bluetooth logger | The record is sent wirelessly to a phone or tablet, and can also be read over USB Type-C | Unit A56 BT |
| Bluetooth logger with external sensor input | Measurement is taken by a remote sensor while the body stays outside | Unit A57 BT |
Selection criteria
- Measuring range: The product data gives −40 °C to 80 °C for the UT330B, and −40 °C to 85 °C and 0–100 % RH for the A56 BT and A57 BT. For extreme environments such as freezers or hot processes, confirm the range in the datasheet.
- Accuracy: For the A56 BT and A57 BT, humidity accuracy is given as ±2.5 % RH at 0–90 % RH and ±3.5 % RH at 90–100 % RH (at 25 °C). Humidity accuracy drops at the very humid end; compare it with the accuracy your specification requires.
- Data transfer: If reading the record on a computer on site is enough, choose USB; if you want to read it from a phone without removing the logger, choose a Bluetooth model.
- Sensor position: If you measure inside a cold room, a fridge or a closed container while the body stays outside, the A57 BT with external sensor input fits.
- Logging interval and battery: A short interval uses up memory and battery faster. The manufacturer gives about 2 years of operation for the A56 BT and A57 BT at room temperature with a 15-minute interval and the display, Bluetooth and alarms off.
- Extra features: The UT330C product data lists atmospheric pressure measurement (±3 hPa) and an alarm threshold; the UT330B and UT330C both have temperature and humidity offset adjustment.
Common mistakes
- Placing the logger in front of a door, fan or heat source: The record shows the conditions at that spot, not the room as a whole.
- Not setting the clock and interval before shipment: The record starts with a wrong time stamp and the report becomes invalid.
- Waiting until the memory is full: Some devices stop recording when full; in long monitoring, transfer the record at intervals.
Temperature and humidity data loggers at Welibaba
The Temperature and Humidity Data Loggers category has 4 active products from Unit: UT330B, UT330C, A56 BT and A57 BT. The UT330B and UT330C are listed with prices, and the A56 BT and A57 BT are sold on quotation. For temperature-only and multi-channel logging see the Temperature Data Loggers category, and for a comparison of logger types see the data logger guide.
Frequently asked questions
What is the difference between a temperature and humidity data logger and a thermohygrometer?
A thermohygrometer shows the value on its display at that moment. A data logger stores readings at set intervals with date and time, so graphs and reports can be produced later.
Should I choose a USB or a Bluetooth logger?
USB is enough if the logger will be collected and read on a computer. If it stays in a closed area or a hard-to-reach spot, a Bluetooth model lets you read the data from a phone nearby.
Which model suits measurements in a cold room?
If the body should stay outside, the Unit A57 BT with external sensor input; if the whole device stays inside, the other models that measure down to −40 °C. Before choosing, check the battery's behaviour at low temperature in the datasheet.