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Description and application


The sensor of temperature and relative humidity - KSTH 122 is designed to measure the temperature and relative humidity of the air into air condition ducts. In the application segment of railway vehicles, it is used to measure both of the variables in air condition ducts of train units and carriages and is a part of the temperature and relative humidity control system.

The sensor of temperature and relative humidity - KSTH 122 consists of a plastic connection head and measuring stem, where a printed circuit board with the individual sensors and a converter is placed to establish a communication via the RS 485 bus. The temperature and relative humidity are measured by a common internal sensor whose signal is processed in a microprocessor and is converted to an output signal of MODBUS RT. The sensors meet ingress protection IP 65 according to EN 60 529.

The sensor of temperature and relative humidity - KSTH 122 is designed to be operated in a chemically non-aggressive environment; the use must be chosen with regard to the temperature and chemical resistance of the sensor head and of the individual sensors. The operating conditions to establish the correct function are:

- Ambient temperature in the vicinity of the sensor: -40 to 80 °C

- Relative ambient humidity: 0 to 100 %

- Atmospheric pressure: 87 to 106 kPa


  • The type tests are carried out by a notified body according to EN 50 155 standard, as amended Railway applications – Electronic equipment used on rolling stock, Art. 12.2.7, 12.2.8, 12.2.9, 12.2.11

- Art. 12.2.7, 12.2.8 according to EN 50121-3-2 – Electromagnetic compatibility

- Art. 12.2.9 according to EN 50155 – insulation test

- Art. 12.2.11 according to EN 61373 – shock and vibration tests

The material of plastic box and PCB meet a set of requirements for the R 24 materials according to the Table 5 for the fire hazard level HL1-HL2-HL3 of the EN 45545-2:2014 standard. The materials also meet requirements of the NFPA 130 fire safety standard, as amended.

  • Manufacturer provides EU Declaration of Conformity.
  • Calibration – The final metrological inspection – comparison with standards or working instruments – is carried out for all the products. Continuity of the standards and working measuring instruments is ensured within the meaning of the Section 5 of Act no.505/1990 on metrology. The manufacturer offers a possibility to supply the sensors calibrated in SENSIT s.r.o.’s laboratory (according to requirements of the EN ISO/IEC 17025 standard) or in an Accredited laboratory.

  • Specifications
  • Wiring diagram
Sensor type KSTH 122
Temperature measurement range -40 °C to 125 °C
Temperature measurement accuracy ± 0.2 °C in range 0 °C to 60 °C
± 1.75 °C inrange -30 °C to 80 °C
Relative humidity measurement range 0 to 100 %
Relative humidity measurement accuracy ± 1.8 % RH in +23 °C (0 to 90 % RH)
± 4 % RH in range 0 to 100 %
Output signal RS 485 / MODBUS RTU
Supply voltage U 15 to 30 VDC
Rated supply voltage Un 24 VDC
Consumption maximum: 500 mW
typical: 250 mW
Ingress protection of the terminal block
IP 65 in accordance with EN 60529
Ingress protection of the sensors
IP 65 in accordance with EN 60529
Sensor dust filter
Filtration capacity 0.025 mm
Dimension of the head 70 x 63 x 34 mm
Standard stem length 100 mm
Material of the head LEXAN (meets standard EN 45545-2)
Weight min 50 g
Recommended wire cross section 0.14 to 1 mm2


Shock and vibration tests

category 1, class B in accordance with EN 61373
Elektromagnetic compatibility in accordance with EN 50121-3-2
Insulation test 1.5 kVDC for time 1 minute in accordance with EN 50155
Fire protection resistance
in accordance with EN 45545 (possible acc. to NFPA 130)

Note: Manufacturer reserves the right to make changes in design and technical characteristics of the products. For actual information, please always contact your dealer.

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