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HT20 Temperature & Humidity Monitor/Data Logger

With Ethernet and PoE

  • Measure, monitor and record temperature and humidity parameters
  • Power over ethernet
  • Built in web server
  • Email and local audible alerts

Product description

The HT20 has been designed to measure, monitor and record temperature and humidity. It is a perfect solution for any facilities where monitoring and recording such values are important for the accuracy of the whole process (for example in server rooms, drug and food warehouses, laboratories, museums or glasshouses).  The data captured by HT20 is stored in the internal memory and then sent digitally to the user (via Ethernet). In case of an emergency situation the device immediately sends appropriate warnings via emails or via its own dedicated website. An additional advantage of HT20 is the possibility that it can be powered over the Ethernet. This feature is available in versions that are equipped with the Power over Ethernet system (PoE).



What parameters
can be measured by HT20?

How does HT20 work in case the pre-set parameters are exceeded?

Ethernet interface
and it's functionality

Measurements archive

  • temperature
  • relative humidity
  • dew point
  • absolute humidity or the total mass of water vapour (in grams) present in 1m3 of air in a given temperature
  • wet-bulb temperature
  • vapour pressure or the pressure at which in a given temperature the gas is at an equilibrium with the fluid (equilibrium between evaporation and condensation)
  • enthlapy (total heat content).


The HT20 allows up to two defined warnings.  Whenever the pre-set parameters are exceeded the HT20 will immediately signal this via:

  • emails
  • messages on a dedicated website
  • special symbols on the display
  • audible alerts.  

Therefore every time the HT20 is connected to the Internet you will always have

the most up-to-date information on the actual condition of the monitored facility.

The HT20 is equipped with the Ethernet interface enabling its connection to the local or global network (either LAN or WAN). Thanks to the user-friendly and intuitive ‘www’ server, you will always have access to the information


  • current measurement values,
  • device status.

The ‘www’ server call also allow you to:

  • configure it
  • read the serial number, manufacturing code, software version and bootloader version.

The built-in FTP server allows for fast and easy access to archive data files from the level of web browser or from other FTP clients. The DHCP protocol provides automatic configuration of the monitor in the computer network, whereas the SMTP protocol is responsible for sending the warnings via emails. The HT20 monitor can also work in more extensive systems where the communication protocol Modbus Slave TCP/IP provides a smooth and reliable reading of all current measurement data.

Thanks to the dedicated website, you can also check the archive data using a smartphone, tablet or a PC. There is no need to be worried about insufficient memory on the device; the HT20 has an 8GB internal file system memory where the data form the internal memory buffer (4GB) is automatically recorded as files.  The memory has a form of a circular buffer and after the storage is full, the oldest files are overwritten. The internal archive can be read, copied and/or deleted.



Technical data


Basic parameters

Relative humidity (RH)

0...95 % condensation inadmissible

Basic error of humidity processing

±3% of the range for RH = 10...90% ; ±5% in other range

Hysteresis of humidity measurement

± 1% RH

Basic range of temperature measurement (T)

 -20...60 °C

Basic error of temperature processing

 ±0.6 oC   in range 10...40 °C; ±1.0 °C  in other range

Calculated values

absolute humidity (a) [g/m3] dew point temperature (Td)  [°C]


Digital interface

Interface type

Ethernet 10/100 Base-T

max. number of simultaneous connections  - 10


Rated operating conditions

Supply voltage

6 V d.c. 

or  PoE IEEE 802.3af


Power concumption

< 2 VA

Preheating time

15 minutes

Ambient temperature

– 20...23...60 °C

Relative humidity

< 95%

Protection grade ensured by housing

IP 20

Fixing way

on a wall


<0.3 kg


120 x 80 x 25 mm

Operating position

sensor down


Safety and compatibility requirements

Electromagnetic compatibility

Noise immunity acc. to EN 61000-6-2

Noise emissions acc. to EN 61000-6-4

Pollution grade

2 acc. to EN 61010-1

Installation category

III acc. to EN 61010-1

Maximal phase-to-earth operating voltage

50 V acc. to EN 61010-1

Altitude above sea level

< 2000 m


Parameters of DC adapter (option):


6 V d.c. ± 5%

Max. power


Input voltage

90...253 V a.c.

Operating temperature

 0...40 oC*

External dimensions

63.6 x 29.5 x 45.6 mm*

Cable length

1.4 m  ± 10%*


ɸ 5.5 / 2.1 mm

*   adapter parameters can be changed


Example of remote readout parameters

Remote readout of parameters through ethernet: WWW Server, FTP


Order numbers

Ordering codes




Part number

6 V dc adapter

Voltage: 6 V d.c. ± 5%

Max. power:  6W*

Input voltage: 90...253 V a.c.

Operating temperature:   0...40 o C*

External dimensions: 63.6 x 29.5 x 45.6 mm*

Cable lenght: 1,4 m  ± 10%*

Plug: ɸ5,5 / 2,1 mm

* adapter parameters can be changed


PoE adapter

Input voltage: 100 – 240 VAC

Input frequency: 47 – 63 Hz

Power consumption: 0.35 A max. for 240 VAC

Output voltage: 48 VDC

Output power: 15.4 W

Operating temperature: 0 – 40 ºC

External dimensions: 140 x 65 x 36 mm

Weight: 0.2 kg


Connector for PoE adapter

Cable length: 1.8 m



Ordering information

Please refer to the data sheet for ordering keys and contact us for more information.

Part numbers

Parts Price


HT20 Data Logger, 6V dc


Contact us

If you need any help, you can contact us in one of the following ways:

0116 284 9900

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