1. Overview
The UNI-T UT330+ series digital temperature and humidity meters (UT331+ and UT332+) are designed for high-precision measurement with low power consumption. These meters feature manual and automatic data storage, USB data transfer, USB power supply, backlight alarm, and real-time display. They are suitable for a wide range of applications including factories, laboratories, research institutes, food and health industries, and environmental protection.
The UT331+ and UT332+ models offer enhanced accuracy and a wider temperature measurement range of -20°C to 70°C. They support dual power modes (USB or AAA batteries) and include PC software for data analysis and export.
Figure 1: UNI-T UT331+ and UT332+ Digital Temperature and Humidity Meters
Video 1: Product overview and features demonstration.
2. Safety Information
▲ Warning
A warning identifies conditions and actions that pose hazards to the user. To avoid electrical shock or personal injury, follow these guidelines:
- Inspect the case before using the Meters. Do not use Meters if they appear damaged. Look for cracks or missing plastic. Pay particular attention to the insulation around the connectors.
- Replace the batteries as soon as the battery indicator appears.
- Do not use Meters if they operate abnormally. Protection may be impaired. When in doubt, have Meters serviced.
- Do not operate Meters around explosive gas, vapor, or dust.
- When servicing Meters, use only specified replacement parts.
- Do not use Meters with any part of the case or cover removed.
- Do not clean the sensor with water. Turn to close the protective sensor cover when not in use. To avoid damage to the device, please use with care.
- Never charge the battery.
- Use the approved alkaline battery (AAA 1.5V) only.
- Pay attention to "+" and "-" marks when installing the batteries.
- Close the sensor cover and remove the batteries if Meters are not used for a long time.
3. Meter Description
3.1 Meter Structure
Figure 2: Meter Structure and Button Functions
The meter features a sensor protection cover, a display screen, and various buttons for operation:
- Power on/off button: Turns the meter on or off.
- MAX/MIN: Displays maximum/minimum values.
- STORE: Saves data manually or initiates automatic storage.
- SETUP: Enters setting mode.
- ENTER/DP: Confirms selections or selects dew-point/wet-bulb temperature.
- HOLD: Freezes displayed readings.
- RECALL: Views stored data.
- Backlight button: Turns backlight on/off, activates/deactivates alarm.
3.2 Display Screen
The LCD displays various information including temperature, humidity, dew point, wet bulb temperature, storage group number, MAX/MIN indicators, data hold, units (°C/°F), battery status, and time.
Figure 3: Example Display Screen
4. Setup
To enter setting mode, short press the SETUP button. Use the ▼▲ buttons to navigate and HOLD or ENTER/DP to select/confirm. The setting mode will exit automatically after 15 seconds of inactivity.
- Setting Temperature Unit: In unit setting page, press HOLD or MAX/MIN to select °C or °F.
- Setting Time Interval for Auto Storage: In time interval mode ("int" on LCD), use ▼▲ to change the interval (0s-60min). 00:00 disables auto data storage.
- Upper-limit Temperature & Humidity Setting: Access by pressing SETUP three times. "HI" appears. Use ENTER/DP to switch between temperature, humidity, dew-point, and wet-bulb upper limits, then use ▼▲ to adjust values.
- Lower-limit Temperature & Humidity Setting: Access by pressing SETUP four times. "LO" appears. Use ENTER/DP to switch between temperature, humidity, dew-point, and wet-bulb lower limits, then use ▼▲ to adjust values.
- Sleep Mode Setting: Access by pressing SETUP five times. "SLP" icon shows. Use ▼▲ to set sleep time (5-60mins). Setting to less than 5mins disables sleep function.
- System Time Setting: Access by pressing SETUP six times. Use ENTER/DP to switch between Year/Month/Day/Hour/Minute, then use ▼▲ to adjust values. Confirm with ENTER/DP to store.
- Temperature & Humidity Offset: Access by pressing SETUP seven times. "t-o" appears. Use ENTER/DP to switch between temperature, humidity, dew-point, and wet-bulb offset settings. Use ▼▲ to adjust offset values within -6 to 6.
5. Operating
5.1 Turn on/off Meters
- Long press the yellow power button to turn on the Meters.
- With Meters already turned on, long press the yellow power button again to turn off the Meters.
- After the sleep time is set, Meters will auto turn off if no button is active within the set time.
- To ensure an accurate result, it is recommended to wait for a while before taking readings if the measured humidity & temperature change dramatically.
5.2 Data Hold
- Press the HOLD button to freeze the reading. "HOLD" appears on the LCD.
- Press HOLD again to quit the function.
5.3 Turn on/off Backlight
- Short press the backlight button to turn on the backlight, press again to turn it off.
- Long press the backlight button to activate the alarm (alarm icon appears). Long press the backlight button again to inactivate the alarm (alarm icon disappears).
With the alarm function activated, the red backlight will flash every 500ms if Meters alarm due to upper limit, the blue backlight will flash every 500ms if Meters alarm due to lower limit. If Meters alarm due to upper & lower limit, the red/blue backlight will flash every 500ms in turn and the corresponding icon will light up.
5.4 View Max/Min Reading
- Short press the MAX/MIN button to check Maximum reading, minimum reading and normal test value.
- Long press MAX/MIN to exit the mode.
5.5 View Dew-point Temperature and Wet Bulb Temperature
- Short press ENTER/DP to view dew point temperature, wet bulb temperature and normal temperature.
- For dew point temperature, "DEW POINT" is displayed on the screen.
- For wet bulb temperature, "WET BULB" is displayed on the screen.
5.6 Data Access
Store Data:
- Manual storage: Set time interval to 00:00. In test page, short press STORE to save data manually. The meter flashes and shows the storage area (e.g., LOG 001). UT331+ can store 299 groups, UT332+ can store 999 groups.
- Auto storage: Set time interval to a value other than 00:00. In test page, long press STORE to store data automatically. The storage area will flash at intervals, and Meters will automatically save data in a circular manner at the set interval.
Recall Data:
- Short press RECALL to check recorded data, press again to exit.
- Use ▼▲ to scroll through recorded readings.
- Short pressing ENTER/DP under RECALL mode allows quick review of data (01 to 299/999) and transfer to PC via USB.
- Long press RECALL under RECALL mode to clear all recorded data. The screen will display "dELE" until data is cleared. This action is irreversible.
5.7 USB Communication and Data Transfer
Figure 4: USB connection for data transfer
- USB Power Supply: Connect the USB cable to a PC USB interface or a 5V DC adapter. The meter will automatically switch to USB power supply. Disconnect the USB cable to switch back to battery power. Note: USB voltage over 5V may damage the meter.
- Data Transfer: Data can be transferred to a PC when in RECALL status (short press ENTER/DP) or when the PC software is running and connected.
- PC Software: Download and install the PC software. Connect the USB cable to the computer. Refer to the "Software Manual" in the Help Option of the software for usage.
6. Maintenance
6.1 Replacing the Battery
When the battery indicator appears, replace the batteries promptly.
- Unscrew the battery cover and remove it.
- Replace with four new AAA 1.5V batteries, observing polarity.
- Rejoin the battery cover and tighten the screw.
6.2 Cleaning the Casing
To clean the surface of the meter, use a soft cloth or sponge dampened with a little water, soap water, or mild detergent. Do not wash the meter directly with water, as this may damage the internal circuits.
7. Troubleshooting
Most common operational issues are addressed in the 'Setup' and 'Operating' sections. If the device does not power on, check battery installation and charge level, or try USB power. If readings are inaccurate, ensure the sensor cover is open and allow time for stabilization, especially after significant environmental changes. Consider using the offset settings for calibration if consistently off.
8. Specifications
| Feature | UT331+ | UT332+ |
|---|---|---|
| Test Temperature | -20°C~70°C (±0.5°C) | -20°C~70°C (±0.3°C) |
| Dew Point Humidity | -78.2°C~70°C (±1°C) | -78.2°C~70°C (±0.8°C) |
| Wet Bulb Temperature | -21.6°C~70°C (±0.5°C) | -21.6°C~70°C (±0.3°C) |
| Humidity | 0-99%RH (10%-90%RH ±3%RH; the rest ±3.5%RH) | 0-99%RH (10%-90%RH ±2%RH; the rest ±2.5%RH) |
| Resolution | Temperature: 0.1°C, Humidity: 0.1%RH | |
| Storage Groups | 299 | 999 |
| Temperature Measurement | Switchable temperature/dew point temperature/wet bulb temperature | |
| Manual Storage | Yes | |
| Automatic Storage | Automatic interval storage can be turned on/off (default is off); storage interval time is 0s-60min | |
| Data View | Can view stored data | |
| Unit Settings | °C/°F switchable | |
| Alarm System | The alarm function can be turned on and off (default is off); backlight alarm (upper limit alarm red light flashes at 500ms intervals; lower limit alarm blue light flashes at 500ms intervals) | |
| Max/Min | Yes | |
| Data Retention | Yes | |
| Software Export Data | PC software can view real-time data and export data | |
| Automatic Shut-down | The automatic shutdown function can be turned on/off (default is on); the automatic shutdown time is adjustable from 5min to 60min | |
| Real Time | Real-time system time can be set | |
| Offset Settings | Can set temperature, dew point temperature, wet bulb temperature, humidity offset value (offset range: -6~6) | |
| Backlight | Can be turned on/off (default is off) | |
| USB Powered | Plug in USB to switch USB power supply, USB voltage: 5V | |
| Power | 1.5V battery (R03) x 4 | |
| Display Size | 26.5mm x 35.5 mm | |
| Product Net Weight | 130g | |
| Product Size | 185mm x 54.8mm x 33.8mm | |
| Certifications | CE/RoHS | |
8.1 Package Contents
Figure 5: Package Contents
- UT331+/UT332+ Meter (1 piece)
- Operating Manual (1 piece)
- Cloth Bag (1 piece)
- USB Cable (1 piece)
- 1.5V AAA Batteries (4 pieces)
9. Warranty and Support
The UNI-T UT331+/UT332+ meters come with a 1-year warranty. For detailed warranty terms and conditions, please refer to the official user manual PDF available at User manual (PDF).
For technical support or inquiries, please contact UNI-T directly. Contact information can be found on the official UNI-T website or in the provided documentation.
UNI-TREND TECHNOLOGY (CHINA) CO., LTD.
No. 6, Gong Ye Bei 1st Road,
Songshan Lake National High-Tech Industrial Development Zone,
Dongguan City, Guangdong Province, China
10. User Tips
This section typically provides practical advice from user experiences. As no specific user reviews or Q&A were provided, here are some general tips for using temperature and humidity meters:
- Placement: For accurate readings, place the meter in a location representative of the area you want to measure, away from direct sunlight, heat sources, or drafts.
- Stabilization Time: Allow the meter sufficient time (e.g., 15-30 minutes) to stabilize after moving it to a new environment before taking critical readings.
- Sensor Protection: Always close the sensor protection cover when the meter is not in use to prevent dust and damage.
- Data Logging: Utilize the automatic data storage feature for continuous monitoring, especially in environments like refrigerators, workshops, or server rooms, to track trends over time.
- PC Software: Make use of the PC software for detailed analysis and easy export of data for record-keeping or reporting.
