COMET U3121G – IoT Wireless Datalogger with 4G Modem and External Temperature and Humidity Probe

COMET U3121G – IoT Wireless Datalogger with 4G Modem, External T+RH Probe (Digi/E), Temperature & Humidity, Dew Point, SMS/JSON Alarm 

The COMET U3121G is a modern IoT wireless datalogger with an integrated 4G modem (LTE Cat 1, FDD/GSM/GPRS/EDGE) – a fully autonomous and independent solution for remote monitoring and long-term recording of temperature, relative humidity, and dew point using an external Digi/E probe. Whether for cold chains, warehouses, climate chambers, server rooms, greenhouses, compressors, dryers, pharmaceutical production, or remote sites – the U3121G immediately sends SMS and JSON alarms over 4G when limits are exceeded. Regular JSON data transmission to COMET Database or COMET Cloud (comprehensive monitoring, alarm, and analysis tool) can be configured. Local alarms are indicated via LED, LCD, and buzzer. With memory for 1 million records (non-cyclic) or 600,000 records (cyclic) and a traceable calibration certificate (EN ISO/IEC 17025), it is ideal for quality management, audits, and ISO compliance.

The external Digi/E probe (sold separately) measures temperature and humidity (range & accuracy depending on the probe, typically −30 to +105 °C / 0–100 %RH). The dew point is automatically calculated. Acoustic and optical alarms instantly warn when user-defined limits are exceeded. Min/max values are recorded. The illuminated LCD displays all values simultaneously. The logger operates completely autonomously using its internal battery – no external power supply is required. Data can be downloaded to a PC via USB‑C. COMET Cloud: 3 months free of charge, then 1 credit per year. The supported LTE FDD B1/B3/B5/B7/B8/B20 & GSM 900/1800 MHz modem ensures worldwide coverage and stable data transmission.

The datalogger is maintenance‑free, long‑term stable, and comes with a 3‑year warranty. The included traceable calibration certificate ensures top‑level measurement accuracy from the factory. Configuration is intuitive via LCD or COMET Cloud. Whether used as a mobile remote logger on construction sites, a stationary monitor in remote facilities, or a central monitoring unit in production – the U3121G stands out with precision, autonomy, 4G connectivity, and ease of use. The external probe enables measurements in pipes, ducts, or confined spaces.

Why the COMET U3121G is the best IoT 4G datalogger for T+RH:

• Integrated 4G modem (LTE Cat 1) – SMS/JSON alarm and data transfer without WLAN/LAN
• External T+RH input (Digi/E series) – flexible measurement anywhere
• 1 million data records – non‑cyclic or cyclic logging
• COMET Cloud – full monitoring, alarm & analysis (3 months free)
• Acoustic/optical alarm + LED – instant on‑site warning
• Dew point and all humidity parameters – automatically calculated
• Illuminated LCD – all values visible at once
• Traceable calibration certificate included – EN ISO/IEC 17025
• Autonomous battery operation – no external power required
• 3‑year warranty – COMET quality guaranteed

Technical data U3121G:

• Temperature & humidity: depending on connected Digi/E probe
• Dew point: depending on connected Digi/E probe (±1.5 °C at T<25 °C and RH>30 %)
• Resolution: 0.1 °C / 0.1 %RH / 0.1 °C dew point
• Alarm: acoustic + optical + SMS/JSON via 4G
• Memory: 1,000,000 records (non‑cyclic) / 600,000 records (cyclic)
• Logging interval: 1 s to 24 h
• Measurement interval / display refresh: 0.7 to 5 s
• Display: illuminated LCD
• Communication: 4G modem (LTE FDD B1/B3/B5/B7/B8/B20 + GSM 900/1800 MHz) + USB‑C
• Power supply: internal battery (runtime several months to years, depending on configuration)
• Operating temperature: −10 to +60 °C
• Protection rating: IP20 (device)
• Warranty: 3 years

Perfectly suited for:

• Cold chain & transport monitoring (remote temperature and humidity)
• Warehouse and cold‑room monitoring at remote locations
• Compressed air systems & compressors (remote humidity tracking)
• Pharmaceutical and food production
• Greenhouses & agriculture
• Server rooms and data centers
• Remote monitoring without on‑site Internet
• Quality management & audits

Installation and use – ready in minutes

Connect the external Digi/E probe, insert a SIM card (if desired), activate the battery – done! Set intervals, limits and Cloud/SMS options, start logging – read data via COMET Cloud or USB‑C. The illuminated display and acoustic alarm ensure safe and comfortable operation. Calibration certificate included – ideal for audits and quality management.

Summary:

• The 4G datalogger is designed for recording temperature and humidity using an external probe
• When configured limits are exceeded, SMS and JSON messages can be sent over the 4G data connection
• Measured data can be transmitted to the online COMET Cloud, a comprehensive monitoring, alarm, and analysis system
• Regular transmission of JSON data to the COMET Database can also be configured; the sending interval is adjustable
• Alarms are indicated locally by LED, LCD, and a built‑in acoustic buzzer
• Data logging is stored in non‑volatile electronic memory
• Data can be transferred to a PC using the included USB‑C cable
• The temperature and humidity sensor is not included in the package
• A probe of suitable length and version is available as optional accessory
• The device comes with a traceable calibration certificate stating metrological traceability according to EN ISO/IEC 17025
• When purchasing a new IoT wireless datalogger with integrated modem, you receive 3 months of free COMET Cloud access. One credit is required for a full year of operation in COMET Cloud.

Package contents:

• U3121G
• User manual
• Traceable calibration certificate
• Battery
• Power adapter
• USB‑C cable
• FREE full version of COMET Vision analysis software
• COMET Cloud access for 3 months
• EXTERNAL PROBES NOT INCLUDED
• SIM CARD NOT INCLUDED