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Combined temperature and humidity sensor for vertical wall mounting indoor usage. Communication over RS-485 bus with a simple communication protocol. The sensor can be used separately but it was designed to be connected with the Poseidon family units.

HTemp-485 Box2 Flyer

HTemp-485 Box2 measures temperature and humidity, communicates over 4-wire bus and up to 26 sensors can be connected parallely to a single bus. The sensor is intended for indoor vertical wall mounting.

The busbar uses 4 wires, two with a standard RS-485 line, the other two are used for sensors' power supply. The individual sensors can be powered by an external power source and can be connected by just two RS-485 line wires. RS-485 communication line works up to 1000m distance.

For temperature measuring the thermal sensor uses an integrated element with accuracy of ±0.8°C, humidity is as well measured by an internal sensor with accuracy 5%.


  • Extensive measuring systems with many measuring points
  • Air-conditioning state measuring and measuring of living conditions in intelligent buildings
  • Independent measuring in food warehouses and agricultural crops storage buildings
  • Grocery storehouses and premises
  • Temperature and humidity monitoring in pharmaceutical storages
  • Measuring in residential premises
  • Industrial measuring and regulation
  • Poseidon model 2250 – temperature values transmission over Ethernet or Internet
  • Poseidon model 2250 – logging possibility of up to 100 000 values into internal Flash memory

Basic features

  • Temperature measuring within the range of -10°C to +70°C
  • Measuring the relative humidity within the range of 0% to 100%.
  • Up to 25 sensors connected parallely at one bus
  • Communication and sensor state indication
  • Communication over the RS-485 line (up to 1 000 m distance), simple communication protocol
  • Minimal power consumption, possible power supply by unstabilized voltage
  • The sensor by itself can send a temperature value according to preset time interval, which can be from 1 to 5000 seconds (circa 1 hour and 23 minutes)
  • The sensor address on RS-485 bus can be set by jumpers inside the sensor as well
  • Easy wall mounting
  • The sensor cooperates with Poseidon thermometer

Downloads & Datasheets



Technical specifications


Basic parameters
+ Range of temperature -10°C to +70°C
+ Range of relative humidity 0% to 100%
+ Resolution format 0.01°C / 0.01%
+ Temperature PROBE measurement accuracy +/- 0.75 °C in range -10°C to +70°C
+ Humidity measurement accuracy 5% from range of 0% to 90% of relative humidity
holds for temperature range 15°C to 30°C
+ Measuring speed Respond to query within 50ms at maximum, temperature measuring 1x within a second
+ Communication parameters 9600 8N1
+ Communication line RS-485 / terminations can be activated by an internal jumper
+ Maximum number of sensors max 25 sensors of the HTemp type at one RS-485 line
+ Status indication R/G indicator: blinks at every measuring (red - temperature, orange humidity measuring).
+ Function modes Auto-Report / Question-Answer
  - Auto-Report mode Temperature value is reported automatically at predefined time, period range is 1 .. 255 [seconds]
  - Question-Answer Temperature is reported at request according to protocol
+ Temperature format „*A+028.0C<CR><LF>“ (A is address of temperature measuring)
+ Humidity format „*a048.19%<CR><LF>“ (a is humidity measuring address)
+ Power supply +8V to +30V DC, protection against reversing of polarity
+ Power consumption Typically 10 mA, max. 50 mA (depending on number of sensors on a line)
+ RS-485 line termination Internal resistor 470W,
+ Conductor connection Terminal or RJ45
+ Mechanic shielding, mounting IP 20, wall mounting - cables brought from below or sideways
+ Outside dimensions 80 x 64 x 67 mm




Sensor wiring

Conductors are connected over terminal or RJ45 connector. Both possibilities can be combined.

HTemp-485 Box2 temperature and humidity sensor can be connected to RS-485 bus in various methods:

  • Direct connection over 4 conductors
    For use in extensive storage buildings. It requires experience with RS485 bus. We recommend this option to very skilled users or installation companies.
  • RJ45
    Sensors connection through S-Hub or one thermometer directly to RJ45 connector with RS-485 on Poseidon unit.
  • RJ45 / directly - Connection of more sensors via S-Hub
    You do not need Poseidon B-Cable to connect sensor over TP cable to RJ45. TP cable with RJ45 connector can be connected directly to terminal board. Use "LAST" configuration if you connect only one sensor(connection detail). In case you connect sensors to S-Hub unit, use "MIDDLE"
    (connection detail) configuration for every sensor except the last one.:

    • RJ45 connector wiring to 4 pinsTerminal: GND (-) = RJ45: 7 (brown/white)
    • Terminal: Vcc (+) = RJ45: 8 (brown)
    • Terminal: RS-485 (A) = RJ45: 5 (blue/white) + 6 (green)
    • Terminal: RS-485 (B) = RJ45: 4 (blue) + 5 (green/white)

    You can find direct RJ45 cable connection details on the bottom of the Poseidon B-Cable page.

Sensor address setting

Every sensor on RS-485 line must have its unique addressEach sensor on RS-485 line must have its unique address for communication with RS-485 bus. This address is presented via small or capital letter and is configurable several ways. Details are available in manual

Assigning of RS-485 address to Temp-485 Box2 sensor:

  • Address configuration via terminal jumper (see picture)
  • Setup mode configuration (console setup mode)
  • Configuration command over RS-485

Notice: Address of HTemp-485 Box2 is always combination of small and capital letters, therefore "A/a" combination is always put.


Certificate of calibration

Sensor sample was calibrated in several certification laboratories. .
All calibration protocols are stored in file: HTemp-485_calibration_sheet.pdf


Sensor samples are already available! Products are on stock in several pieces most of the time. The price can be found on the Pricelist page.


OID Device type
600 505
HTemp-485 Box2 - photo
Indoor temperature and humidity sensor with RJ45 and terminal for RS-485 connection

Special accessories

  • Sensor RJ45 MIDDLE cable [600 233] (details)
    About 0.5 meter long cable, connecting 4 pins ( A,B,+,- ) from terminal unit to RJ45 connector. Cable for connection of middle sensors.
  • Sensor RJ45 LAST cable [600 234] (details)
    About 0.5 meter long cable, connecting 4 pins ( A,B,+,- ) from terminal unit to RJ45 connector. Cable for connection of the last sensor in-line.
  • Poseidon S-Hub [600 041] (details)
    RS-485 line switch for 8+1 RJ45 connectors and TP cables. S-Hub can be used as a power supply for all connected sensors.


->Pricelist (ordering) 

How to order

  • ShippingFor ordering from abroad (except Slovakia) we accept payment cards. We support VISA and Eurocard/MasterCard..
  • We deliver within 48 hours from purchase order via FedEx post service
  • Please follow the orders on the ordering page.
    Your order will be confirmed within 24 hours (during weekdays) via e-mail. It will include term of delivery.

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