COMET H3531 – WebSensor, Cable Probe for Temperature, Humidity, 2 Relay Outputs

COMET H3531 – Ethernet sensor with external cable probe for temperature –30 to +105 °C, humidity, dew point + 2 relay outputs 

The COMET H3531 is a professional Ethernet sensor with external cable probe (1 meter standard, optional 2 or 4 meters) for temperature, relative humidity, and dew point – plus two powerful relay outputs. As a true remote thermometer-hygrometer with control functionality, it is the ideal solution for intelligent humidity control and climate monitoring in buildings, warehouses, clean rooms, production facilities, greenhouses, climate chambers, or anywhere humidity must be actively regulated (e.g. humidifiers, dehumidifiers, fans, alarms).

The high-precision capacitive polymer sensor ensures excellent long-term stability and accuracy: temperature up to +105 °C (±0.4 °C), humidity 0–100 %RH (±2.5 %RH from 5–95 % at 23 °C). The dew point is calculated with high accuracy (±1.5 °C at T<25 °C and RH>30 %). All humidity variables (absolute humidity, specific humidity, mixing ratio, specific enthalpy) are directly available. The flexible cable probe enables optimal positioning – ideal for tight, hot, or remote measuring points.

The two relay outputs (max. 50 V / 2 A / 60 VA) can be freely programmed by humidity, temperature, or dew point thresholds – perfect for direct control of humidifiers, dehumidifiers, fans, alarms, or emergency shutdowns. In addition, the H3531 features three binary inputs for monitoring status signals (door contacts, motion detectors, switches, etc.). The large dual-line LCD displays all measured values and relay status.

Via Ethernet (RJ45), the sensor integrates seamlessly into networks – with direct connection to the COMET Cloud (3 months free, then 1 Credit / year) for charts, exports, alarms, and remote access via app or browser. Alternatively, Modbus TCP, SNMP, JSON, or XML can be used for your own BMS/SCADA/IoT solution. Optionally, it can be powered via PoE – just one cable for data and power.

The robust housing (IP30 electronics, IP65 probe) and the operating temperature range from –30 to +80 °C make the H3531 a reliable partner for demanding long-term use – indoors or outdoors. The sensor is maintenance-free, long-term stable, and the first choice for humidity control with external probe.

Why the COMET H3531 is the professional hygrometer with relay outputs:

• External cable probe 1–4 m – maximum flexibility at measuring points
• 2 relay outputs – 50 V / 2 A – for direct humidity control
• 3 binary inputs – for status monitoring
• Ethernet interface – direct network integration
• COMET Cloud ready – 3 months free, low cost afterward
• Modbus TCP, SNMP, JSON, XML – open to third-party systems
• Large dual-line LCD – shows values + relay status
• Highest precision – Temp. ±0.4 °C | Humidity ±2.5 %RH | Dew point ±1.5 °C
• All humidity variables integrated – dew point directly available
• Remote alarm function – email, SNMP trap, Syslog
• IP65 probe – for humid & dusty environments

Technical data H3531:

• Temperature range: –30 to +105 °C (±0.4 °C)
• Humidity: 0 to 100 %RH (±2.5 %RH from 5–95 % at 23 °C)
• Dew point: –60 to +80 °C (±1.5 °C at T<25 °C and RH>30 %)
• Relays: 2 × max. 50 V / 2 A / 60 VA
• Binary inputs: 3 × (dry contact, open collector, or voltage signal)
• Probe cable length: 1 m (standard), optional 2 or 4 m
• Interface: Ethernet (RJ45)
• Cloud: COMET Cloud (3 months free)
• Protocols: WWW, Modbus TCP, SNMPv1, SOAP, XML
• Alarm protocols: Email, SNMP Trap, Syslog
• Power supply: 9–30 V DC (PoE optional)
• Operating temperature: –30 to +80 °C
• Protection: IP30 electronics, IP65 probe
• Warranty: 3 years

Perfect for:

• Building automation and BMS systems
• Data centers and server rooms
• Clean rooms and pharmaceutical production
• Food storage and cold rooms
• Museums, archives, and depots
• Humidity control with external probe
• Climate chambers and drying plants
• Comfort & workplace monitoring

Installation & commissioning – done in minutes

Mount the device, connect network cable and power, place the probe at the desired location, wire the relays – done! The integrated web interface guides you through setup and relay configuration. Online with COMET Cloud in seconds – no server effort required.

Available versions:

• Cable length 1 meter
• Cable length 2 meters
• Cable length 4 meters

Summary:

• Humidity, temperature, and Humidex Ethernet sensor with cable and two relay outputs
• The Humidex sensor H3531 is used for online monitoring of temperature, relative humidity, and Humidex of air without aggressive substances
• Three binary inputs for detecting two-state signals offer a major advantage
• The two relay outputs allow control of external devices
• The highly accurate capacitive polymer sensor guarantees excellent long-term calibration stability and top accuracy
• The measured values are converted into other humidity parameters: dew point temperature, absolute humidity, specific humidity, mixing ratio, and specific enthalpy
• The device is delivered with a temperature and humidity probe with 1 m cable. Cable lengths of 2 m or 4 m are optionally available.

Scope of delivery:

• H3531 – probe cable length as selected above
• Operating manual
• Traceable calibration certificate
• Free TSensor software for transmitter configuration
• COMET Cloud for 3 months
• Power supply not included