COMET U3121M – IoT Wireless Datalogger with 2G Modem, External Temperature and Humidity Probe

COMET U3121M – IoT Wireless Datalogger with 2G Modem, External T+RH Probe (Digi/E), Temperature & Humidity, Dew Point, SMS/JSON Alarm 

The COMET U3121M is the reliable IoT wireless datalogger with an integrated 2G modem (Quad-Band GSM/GPRS) – the self-sufficient 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 U3121M immediately sends SMS and JSON alarms via GPRS when limits are exceeded. Regular JSON data transmission to COMET Database or COMET Cloud (comprehensive monitoring, alarm, and analysis tool) can be configured. On-site alarms are indicated via LED, LCD and buzzer. With 1 million data points of non-cyclic memory or 600,000 cyclic values 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 probe, typically -30 to +105 °C / 0–100 %RH). The dew point is calculated automatically. Acoustic and optical alarms instantly warn when freely adjustable limits are exceeded. Min/max values are recorded. The illuminated LCD displays all values simultaneously. The logger operates completely independently with its internal battery – no external power supply is required. Data download via USB-C to PC is possible. COMET Cloud: 3 months included free of charge, then 1 credit/year. The GSM modem (850/900/1800/1900 MHz) provides global coverage. GPRS Class B ensures stable data transmission.

The datalogger is maintenance-free, long-term stable, and comes with a 3-year warranty. The included traceable calibration certificate guarantees top 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 unit in production – the U3121M impresses with precision, autonomy, 2G connectivity, and simple handling. The external probe enables measurements in pipes, ducts, or confined spaces.

Why the COMET U3121M is the best IoT 2G datalogger for T+RH:

• Integrated 2G modem (Quad-Band GSM/GPRS) – SMS/JSON alarm & data transfer without WLAN/LAN
• External T+RH input (Digi/E series) – flexible measurement anywhere
• 1 million data points memory – non-cyclic or cyclic
• COMET Cloud – full monitoring, alarm & analysis (3 months free)
• Acoustic/optical alarm + LED – instant on-site warning
• Dew point & all humidity parameters – automatically calculated
• Illuminated LCD – all values visible at once
• Traceable calibration certificate included – EN ISO/IEC 17025
• Battery-operated autonomous unit – no external power required
• 3-year warranty – COMET quality guaranteed

Technical data U3121M:

• Temperature & humidity: according to connected Digi/E probe
• Dew point: according to 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 GPRS
• Memory: 1,000,000 values (non-cyclic) / 600,000 values (cyclic)
• Logging interval: 1 s to 24 h
• Measurement interval / display refresh: 0.7 to 5 s
• Display: illuminated LCD
• Communication: 2G modem (Quad-Band 850/900/1800/1900 MHz, GPRS Class B) + USB-C
• Power supply: internal battery (lifetime depending on configuration – several months/years)
• Operating temperature: -10 to +60 °C
• Protection: IP20 (device)
• Warranty: 3 years

Perfectly suited for:

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

Installation and operation – done in minutes

Connect the external Digi/E probe, insert the 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 make operation safe and convenient. A calibration certificate is included – ideal for audits and quality management.

Summary:

• The GSM datalogger is designed for recording temperature and humidity via external sensors
• When the set limits are exceeded, SMS and JSON messages can be sent via GPRS data connection
• The measured values can be sent to the online COMET Cloud, a comprehensive monitoring, alarm and analysis system
• Regular transmission of JSON messages to the COMET database can also be configured; the sending interval is adjustable
• Alarms are indicated locally via LED, LCD and an integrated buzzer
• Recording 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
• A probe of suitable length and type is available as optional accessory
• The device includes a traceable calibration certificate declaring metrological traceability of standards 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 COMET Cloud operation.

Package contents:

• U3121M
• User manual
• Traceable calibration certificate
• Battery
• Power adapter
• USB-C cable
• Full version of COMET Vision analysis software (free)
• COMET Cloud for 3 months
• External probes not included
• SIM card not included