Index >> Products >> Monitoring >> Poseidon xxxx

Poseidon2 4002: Data center environment monitoring

Poseidon2 4002 is a system for remote monitoring of rack environmental conditions (occupies 1U). Measures temperature, checks if the lights are on or the doors are open in the server room, and more. Relay outputs (4x digital output) can activate fans or an additional light. Poseidon is SNMP compatible, includes a data logger, e-mail and SMS alerts. It can be connected to the SensDesk online portal or cloud sensor systems.

Poseidon2 4002 is a remote environment monitoring system for datacenters and server rooms.
It alerts to open door, high temperature and humidity, or other sensor readings. Typical applications include monitoring one or more racks, or the entire server room. Poseidon2 4002 can be mounted on the wall, on a DIN rail, or as a 1U device in a 19” rack.

Use your Poseidon to monitor your computer room temperature via SNMP (Nagios, Cacti, OpenView, ..) or with a smartphone app.

Poseidon2 4002 can be used as a standalone environment monitoring device with email alerts or as a part of a complex monitoring system (SNMP or SensDesk online portal).

Sensors and detectors

Up to 16 external sensors, 12 detectors with a dry contact output, 4 relay outputs and a GSM modem can be connected.
We supply temperature and humidity sensors (indoor/outdoor), light intensity sensors, DC/AC current and voltage converters.

Digital Inputs can be connected to smoke detectors, power failure detectors, water flood detection, and more. Relay outputs can be controlled over the Web, or according to the value of a connected sensor, for example to control air conditioning or ventilation.

E-mail and SMS alerts

When a value is out of a specified range, Poseidon2 sends an e-mail, a SNMP Trap, or a text message (SMS). Text messages (SMS) can be sent via an external GSM modem, or through a central “HWg-SMS-GW” text message gateway. Just a single SIM card can serve all your devices.

Web interface, software, mobile apps

The device can be accessed over the web, using a mobile phone app (Android, iPhone), or through an online portal. Temperature alarms, for example, can be sent by e-mail or SMS.

For data collection and monitoring, we recommend our HWg-PDMS application that displays graphs and exports data to MS Excel.
For “IF-THEN” event management (e.g. “If one out of 10 devices fails, send a SMS to the admin”), we provide the “HWg-Trigger” application for Windows.

For remote monitoring of several sites, the online service can be used. It can display readings from sensors at multiple Poseidon2 units and other HW group products on a single screen. The online portal is configured over the web and all devices can monitored with a mobile phone app.

Poseidon2 can be connected to various monitoring systems. We support over 50 different third-party SNMP or SCADA applications.

Poseidon2 4002: Environment monitoring in a data center – designed for 19" cabinets
Poseidon2 3268: Ethernet I/O control and sensor monitoring system

Poseidon2 3268: Ethernet I/O control and sensor monitoring system

Front view    Rear view    Wall montage

  DIN rail    DIN holder    Rack 1U bracket   Rack 19" 

   Poseidon2 4002 Tset    Package 

Poseidon2 4002 & GSM modem in Rack Shelf 1U


  • Ethernet: RJ45 (10/100 BASE-T)
  • WEB: Built-in web server
  • Data logger: Data logger for more than 250.000 records
  • Sensors: 6xRJ11 – max. 16 external sensors (1-Wire / 1-Wire UNI)
    Can measure: humidity, voltage, current, 4-20mA, illumination, temperature (incl. Pt100, Pt1000) and many other quantities...
  • Digital inputs (DI): 12x DI for dry contacts (state detectors)
    Supports: Door contacts, smoke detectors, 110/230V power supply detector, water leak detector, fan failure detector
  • Digital outputs (DO): 4x DO relay output (low-voltage NO/NC relay contact)
  • RS-485 support: Yes, external sensors by HW group can be connected
  • Power: 9-30V DC
  • Mechanical: Metal housing 100 x 213 x 35 [mm] – can be mounted on a wall, on a DIN rail, or as a 1U device into a 19" cabinet.
  • Operating temperature: –30°C to +85°C (-22°F to +185°F)

  • Warranty: 5 years
  • M2M communication protocols: SNMP (version 1 & 3), XML, Modbus/TCP, HWg-Push
  • Cloud support: HWg-Push protocol
  • GSM modem: An external GSM modem for sending text messages (SMS) can be connected to RS-232
  • SMS + ring upon alert: Supported
  • Text messages (SMS): Alerts can be sent as SMS (text messages) with up to 5 recipients (phone numbers).
    SMS can be sent through a local GSM modem or a remote „HWg-SMS-GW“ over the network. No software is needed.
  • Support for programmers: HWg-SDK
  • Recommended online portal: – free online portal
  • Supported software
    • HWg-Trigger: Control of other IP devices, alarm redirection to SMS
    • HWg-PDMS: Logging, export to MS Excel, reports
    • Third-party software (SCADA systems, Modbus/TCP)

Data logging

  • Poseidon2 includes an internal flash memory for the data logger. Data are kept even if the power goes off.
  • The logger has a capacity for 250,000 records. For Poseidon2 4002 working as a temperature logger with one temperature sensor and 4x DI, this means enough memory for 230 days (7.5 months) when logging every 300 [s] (5 minutes).

Tip: The HWg-PDMS application can, for instance, read data from the internal memory over e-mail or web interface.

Usage examples

  • Server room environment monitoring
    • Temperature in a 19" cabinet and in the room
    • Remote environment monitoring (lights, power, fire protection system, ...)
    • IT monitoring of security systems (alarms, room / cabinet doors monitoring, ...)
  • Remote environmental monitoring in a cabinet or in a datacenter
    • Temperature and humidity in the datacenter (inside racks, in the A/C outlet, under the raised floor)
    • Detection of redundant power failures
    • SNMP (SNMPv3) environment monitoring system
  • Air-conditioning monitoring
    • A/C, temperature, humidity monitoring
    • Control of additional cooling in a room or in a rack
    • Alert to leaking water
  • UPS / back-up generator monitoring
    Fuel level, diesel generator status, remote start over IP, monitoring of temperature and service contacts

  • Remote I/O control and monitoring over the Ethernet
    Monitors a remote environment, sensor values can be fed into any SNMP system. Enables remote reading of dry contact inputs and remote control of relay outputs (to turn on HVAC, restart a server, start a diesel generator, ...).

  • Industrial applications
    Remote monitoring of dry contacts, 4-20mA sensors or Pt-100 and Pt-1000 temperature probes.
    Data logger stores the values in the internal memory. Modbus/TCP protocol can be used for integration with SCADA systems.
  • Cooler and freezer monitoring + alarm indication
    Measures temperature and humidity in a cooler or a freezer. When a value is out of a safe range, a relay output is activated to e.g. turn on a warning light or sound a horn. Suitable for monitoring storages of food or pharmaceuticals. We recommend the PDMS software to monitor temperature.

  • Temperature and other measurements in a cloud
    Poseidon2 remote monitoring device can be connected to cloud systems. Contact us for details.
  • Surveillance systems
    Sensor readings and detector states can be fed to IP camera systems of various brands. Digital Outputs can be used to turn on the lights in a certain zone or open/close gates.

  • Smart buildings
    Sensor readings can be shared in several applications. Relay outputs can be controlled as remote I/O.

Server room: environment monitoring in the room

Controlling back-up A/C + remote environment monitoring
  • When the main A/C in the server room fails (temperature in the room becomes too high), Poseidon2 4002 turns on back-up A/C and alerts the operator.
  • Poseidon2 logs every opening of room or rack (cabinet) doors, can also send an e-mail.
  • Many customers use e-mail alerts and detection of light turned on in a room to detect the arrival of an operator.
  • Remote environment monitoring (humidity, power status, smoke detection, battery state measurement).
  • Water leak detection with a 2D water leak detector (WLD) on the server room floor. Leaking water can be detected with the sensing cable at multiple places and detection zones.
  • Humidity and temperature sensor monitors the dew point and operational conditions of supplementary air-conditioning.
  • Smoke detector is powered directly from the power-out output of Poseidon2 4002, no additional power adapter is necessary.
  • Server room status can be checked remotely in a smartphone app (available for Android and iPhone).
  • Server room alarm monitoring can also take place over the web or e-mail.
  • For remote monitoring of several datacenters, you can use the online portal and monitor your devices with SensDesk mobile (mobile app for Android and iPhone).

Rack (cabinet): Remote environment monitoring

  • Connecting I/O to a CCTV system Poseidon2 4002 monitors the rack environmental conditions:
    • Temperature too high at the air inlet/outlet
    • Front/rear door opening
    • Light turned on in the server room
    • UPS status (power outages)
    • Smoke detector
    • Temperature at critical points (disk arrays, servers)
  • Relay outputs of Poseidon2 4002 can control:
    • Remote server restart
    • Fans
    • Light tower / cabinet indicators
    • Rack door lock
  • Temperature sensors can be placed outside the rack and measure e.g. the room temperature or the temperature in another rack.
  • To evaluate alarm situations and send alerts, we recommend the HWg-Trigger app for Windows.
  • Poseidon logs the values to its internal memory. The log can be displayed and processed e.g. in the HWg-PDMS utility for Windows.
  • Remote environment monitoring in a datacenter over SNMP
  • Can be connected to BMS (Building Management System) or SCADA (Modbus/TCP).

SMS alerts: One SIM card for all your devices

Sensors and I/O over Ethernet
  • Poseidon2 4002 with a GSM modem can work as a SMS gateway for all your other HW group monitoring devices in the same LAN.
  • Poseidon2 4002 with a GSM modem is a "SMS Gateway" for other devices – just as the dedicated “HWg-SMS-GW” product. Poseidon2 4002 offers somewhat lower throughput in terms of SMS per minute.
  • Works entirely at the hardware level – as long as the LAN works, text message alerts will be sent.
  • "Power OUT" terminals at the Poseidon unit can be used to power the GSM modem.

Multiple rack monitoring: 6 racks (12 sensors) monitored by a single Poseidon2 4002

  • Poseidon2 4002 is located in one of the racks, where it also monitors the door with a door contact.
  • The other five racks are equipped with a temperature and humidity sensor.
  • Sensors are daisy-chained. Several sensors can be connected to a single active RJ11 port on the Poseidon2 4002.
  • CAT5 cabling can be used to connect sensors in external racks.
  • Temperature/humidity sensor can be also placed in the room, or at an air-conditioning outlet.

Detectors (most popular)

FDR26 Smoke Detector

Smoke detector (12VDC power, relay output)

Door Contact

Open door detector

Impaq shock sensor

Vibration detector (12VDC power, relay output)

Gas Leak Detector

Detector of flammable gases (12V, relay output)


Power failure detector (relay output)

Motion PIR detector

Motion detector (12VDC power supply)

>> Overview of all sensors and detectors

Sensors (most popular)

Converter 2xPt100 1W-UNI

2x temperature (external temperature probes)

  • -200°C to +850°C (-330°F to +1560°F)
  • Connect up to 2 Pt-100 or Pt-1000 temperature probes

Temp-485-Pt100 Box

Outdoor temperature sensor (RS-485 bus)

  • -25°C to +80°C (–13°F to +175°F)

PHTemp-485 T7410

Temperature + humidity + atmospheric pressure + dew point
RS-485 bus

Expander 4xDI 1W-UNI

4x DI (dry contact input) to RJ11

  • RJ11 1-Wire UNI (needs 4 positions)
  • Designed for indoor use

HWg-WLD Relay

Detects flood in a 2D area using a cable

  • RJ11 1-Wire UNI (includes power)
  • Supplied with 2m detection WLD cable

Sensor 60V 1W-UNI

Measures voltage, 0–60VDC

  • Electrically isolated
  • Recommended for measuring –48VDC

30A Current probe 1W-UNI

0–30A AC current sensor for indirect measurement

  • 0-30A current measurement using a split-core transducer
  • Installation without disconnecting the measured circuit

Sensor Light 1W-UNI 3m

Illumination intensity sensor with a 3m cable

  • Indoor use
  • Output 0–100%

Sensor 4-20mA 1W-UNI

Measures 4–20mA DC current

  • Electrically isolated
  • Power for an external 4-20mA probe

HTemp-1Wire Outdoor 3m

Temperature + humidity (outdoor)

  • –30 to +85°C (–22 to 185 °F) 
  • 0-100% RH   (Relative Humidity)

HTemp-1Wire 3m

Temperature + humidity (indoor)

  • –30 to +80°C (–22 to 175 °F) 
  • 0-100% RH   (Relative Humidity)

Temp-1Wire-Flat 3m

Temperature (in coolers and freezers).

  • –30 to +60°C (–22 to 140 °F) 
  • IP67, 17240 stainless steel probe – Ø5.7mm
  • Flat cable for installation in a cooler

Humid-1Wire 1m
Humid-1Wire 3m
Humid-1Wire 10m

Humidity (indoor)

  • 0-100% RH   (Relative Humidity)


Temperature + humidity (1U size for 19" rack mount)

  • –10 to +80°C (+14 to 175 °F)
  • 0-100% RH   (Relative Humidity)

Temp-1Wire 1m IP67
Temp-1Wire 3m IP67
Temp-1Wire 10m IP67

Temperature (indoor and outdoor)

  • –10 to +80°C (+14 to 175 °F) 

>> Overview of sensors

Software and applications

>> Software and applications

HWg-Trigger: Alarm monitoring and events

With the PD Trigger application for Windows, it is possible to receive alarms (SNMP traps) from an unlimited number of Poseidon products and define conditions and actions based on the originating device and the probe name. For example:
  • In case of air conditioning failure in server room A, send a SMS to Peter
  • In case of alarm in server room B, send e-mail to Tom
  • In case of electricity supply failure anywhere, send SMS to Peter and turn on a warning light at the receptionist's desk

Poseidon 4002: rack mount environment monitoring, e-mail alerting, sms alerts

>> Software for the Poseidon family

Connection to the online portal

  • Poseidon2 4002 can be connected to the online portal.
  • All devices, sensors, values, history and charts can be viewed from anywhere over the web, or in a mobile app (for Android and iPhone).
  • For programmers: Devices connected to the portal can be monitored using a XML interface.
  • Cloud sensor: Poseidon2 can be connected to sensor cloud systems. Contact us for details.

Poseidon2 connected to a cloud system

Text message (SMS) alerts

SMS alerts can be sent from the Poseidon2 4002 remote monitoring unit to mobile phones in several ways:

  • Using an external GSM modem
    An external GSM modem can be connected to Poseidon2 4002 over the RS-232 interface.
  • Over the LAN: using another Poseidon2 4002 with a GSM modem
    SMS alerts can be also sent through another Poseidon2 4002 unit that has a GSM modem connected to it. Both units must be in the same LAN.
  • Over the LAN: using a HWg-SMS-GW unit
    SMS alerts can be sent to the destination phone number using a “HWg-SMS-GW” unit in the same LAN (Local Area Network).
    No software is needed. Sender's phone number is defined by the SIM inserted in the HWg-SMS-GW unit. Recipient's phone number is configured in the Poseidon2 4002 unit that sends the alert (similarly to e-mail recipients). One HWg-SMS-GW unit can be used by several "SMS Client" devices.
  • With the HWg-Trigger application for Windows
    The HWg-Trigger application can run in the background on any PC with MS Windows. The application checks for device failures, disconnected sensors, or sensor readings outside of the Safe Range. Alarm status can be notified e.g. by sending a SMS to a specified number using a “HWg-SMS-GW” in the same LAN.
  • With third-party software applications
    Many SCADA (e.g. CapTemp) or SNMP (Nagios, Zabbix, ..) applications can monitor the status of Poseidon2 4002 units and send alerts via SMS.

Frequently Asked Questions

    Ask for the price or details:
     - Web:  http://
    Country: *

    Spam protection. How many is SIX times six?

  • Does the Poseidon2 4002 package include the mounting brackets for a 19" rack?
    In the package under the "Poseidon2 4002 Tset" ordering code, the mounting elements for a 19" rack are included.
    The product under the "Poseidon2 4002" ordering code does NOT include the mounting kit. If you need it, order the "Rack mounting brackets 19" item as well.
  • What is the maximum number of e-mail recipients for alerts?
    Poseidon2 itself can send e-mails to at most 5 e-mail addresses.
    With the online service or the HWg-Trigger application for Windows, e-mails alerting to OK/Alarm states can be sent to more than 5 e-mail addresses.
  • Poseidon2 4002 supports 16 sensors but features only six RJ11 connectors. How can I connect more sensors?
    Sensors can be daisy-chained, or connected to a hub: T-Box2 (photo), T-Box (photo) or 1-Wire hub Power.
  • How many temperature/humidity combo sensors can be connected?
    Poseidon2 4002 supports 16 sensors (measured quantities). Combined temperature + humidity sensor measures two quantities. Only at most 8 combined temperature/humidity sensors can be connected to Poseidon 4002.
  • What can I measure with Poseidon2 4002?
    Indoor/outdoor temperature and humidity, light intensity, 0-10VDC or 0-60VDC (-48VDC) voltage, 0-30AAC current, 4-20mA current, Pt-100 and Pt-1000 external temperature probes, DI (digital inputs), analog PTC and NTC. For details see Overview of sensors.
  • How far can I connect the external sensors?
    1-Wire sensors: Each active port (RJ11 connector) of the Poseidon2 unit supports sensors at 60m maximum distance.
    Some sensors might require boosted power.
    RS-485 sensors: Total bus length is limited to 1000m. The bus must be properly terminated with resistors.
  • I found the 4-20mA sensor, but how can I measure 0-10VDC or -48VDC with Poseidon?
    Use the 0-60VDC sensor, the measurement accuracy is good enough even for the 0 to 10V range.
  • Can Poseidon2 4002 measure energy consumption?
    Yes, it can measure the immediate current or voltage.
    To measure energy consumed over a time period, e.g. [kWh] or [J], we recommend to use the HWg-PWR 3/12/25 device and a M-Bus enabled electricity meter, gas meter, water meter or heat meter.
  • Why does the unit have the Power-Out?
    A typical application involves the use of an external smoke detector, motion sensor etc. These external sensors feature a relay output that connects to IN1 – IN12. However, external detectors need power (typically 12VDC). The Power-Out terminal block is convenient for connecting a power adapter (jack) for powering the external detectors.
  • How can I create a graph or a report with recorded temperatures?
    Use the HWg-PDMS software utility for Windows. Values recorded in the database can be displayed or exported to MS Excel.
    Or, use a suitable third-party software. For a list of over 50 third-party applications, see: Third-party software
  • Do you offer a SW solution that will alert me to an outage of a Poseidon2 unit?
    Yes, you can use the HWg-Trigger application that runs on any Windows PC.
    Another option is the online service – free portal for IP sensors.
  • Is there an app for my mobile phone?
    Yes, several third-party apps for Android and Apple are available here: Android and iPhone mobile app for HW group products
  • The humidity sensor reading oscillates around the specified SafeRange and I received over 50 e-mails in a single hour. What can be done about it?
    Set the hysteresis for this sensor to about 5% RH. This reduces the number of unnecessary alarm start/end e-mails that would be sent a couple of seconds one after another.
  • Will I lose data in the internal memory (log file) if the power is disconnected?
    No, stored data are protected against power failures. When the memory is full, the data logger overwrites oldest data with new data.
  • Can Poseidon2 4002 detect the presence of 230VAC (e.g. the input voltage of an UPS)?
    Yes, use the input voltage detection feature of the PowerEgg2 unit, or any relay with a contact connected to one of the IN1-IN12 “Dry Contact” inputs.
    A relay output of a Poseidon2 4002 can control a 110/230V output of a PowerEgg2.
  • Can I connect voltage detection to DI (“wet contact”)?
    No, digital inputs (DI) are designed for direct connection of a voltage-free contact (“dry contact”), such as a door contact or a relay output.
  • Poseidon2 4002 features 12 digital inputs for dry contacts (IN1-IN12). Is it possible to extend the number of DI inputs?
    Yes, use the Expander 4xDI 1W-UNI module – however, it counts as 4 sensors.
  • Can I control the relay outputs over the Poseidon2 4002 web interface?
    Yes. If the DO is in the “Local condition” mode, turn off this mode first.
  • Can I control a relay output with a sensor? For example, turn on A/C if the temperature exceeds 35°C?
    Yes, the output can be controlled with a "local condition". We call this the “Thermostat mode”.
    It is configured on the “Outputs” tab, including the thresholds (e.g. 35°C) and the sensor.
  • Can I control a 110/230V relay over IP?
    Yes, the relay output of a Poseidon2 4002 can be controlled over IP using M2M protocols (Modbus/TCP, SNMP, SNMPv3, HTTP/XML and more), acting as an IP relay for 110V or 230V.
    Use a PowerEgg2 unit to control a 110/230V output.
  • Is it possible to connect Poseidon2 4002 to a cloud?
    Yes, Poseidon2 is a “cloud oriented sensor”. It can be connected to cloud systems as a “Cloud sensor”.
    Use the HTTP-based HWg-Push protocol. Contact us for details.
  • Is it possible to use SNMP monitoring and connection to SensDesk at the same time?
    Yes, Poseidon2 can be connected to a SNMP remote monitoring system in a data center and at the same time to the SensDesk online service.
  • What is the warranty?
    The standard warranty is 2 years, can be extended upon request.
  • Where can I find the prices of your devices?
    Ask our distributors, or request a quote from us (by e-mail or by filling out this form).

>> Online order form




Product Description
Poseidon2 4002 Tset Poseidon2 4002 quick start set
Bracket for a 19" rack, power adapter, Temp19 rack temperature sensor + temperature sensor on a 3m cable, door contact, Poseidon2 4002 unit, screwdriver. - product photo
Poseidon2 4002 Poseidon2 4002 unit only.
Poseidon2 4002 unit with no accessories. Data center environment monitoring system. 12 digital inputs, 4 digital outputs (relay), 6x RJ11 for up to 16 sensors (1-Wire / 1-Wire UNI). - product photo

Power adapter, sensors and 19" rack bracket are NOT included under this ordering code.
Rack mounting brackets 19" Brackets and accessories for mounting a Poseidon2 4xxx or HWg-SMS-GW2 unit into a 19" cabinet. - item photo
Rack Shelf 1U Profile and accessories for two or more devices installed to one 19” 1U cabinet position. Installation manual / product photo
Mount plate D Bracket for attaching HWg-Ares, Poseidon2 3266/68 or other products to a wall. - item photo
PowerEgg2 110/230VAC voltage sensing and control.
IEC-320 power connectors. Electrically isolated relay output (DO) to detect power, dry contact input (DI) to control the 230V output. - product photo
GSM Quadband TC55i TC55i GSM Quadband modem for a RS-232 serial port. Includes an external antenna and an EU power adapter. Suitable for use in North and South America as well. - product photo
HWg-SMS-GW2 Central SMS Gateway - start set
GSM SMS gateway for sending text messages from other HW group devices over the LAN. Includes an internal GSM modem, an external antenna with 3m cable, a power adapter and a CD. - photo


Poseidon2 accessories


>> Order



Poseidon2 4002, data center environmental monitoring, server room alarm monitoring, rack environmental conditions, temperature and humidity, computer room temperature, room alert, environment monitoring system,

email alert, smoke detector, temperature logger, current sensor, voltage sensor, temperature sensor, water leak detector, temperature measurement, door contact, server monitoring, environmental monitoring, snmp, network cabinet, remote monitoring, cabinet doors monitoring, 1u server room monitoring, sms alarm, SNMPv3

Similar and related products


Product banners