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Description and application


ST 485C and STD 485C converters are intended for converting the signal of Pt 1000/3850 resistance-type temperature sensing elements to the digital signal of RS 485 serial bus. The standard temperature range is -50 °C to 150°C. Communication inputs are protected to overvoltage. In case the module is placed as terminal on the line, a terminating resistor can be attached to the wiring by shorting the contacts (the switch SW placed next to terminals for communication lines connection). All settings are stored in EEPROM memory. The electronic module is equipped with the WATCHDOG circuit, which safeguards proper program functioning in the microprocessor. These converters can be utilised in any control system compatible with communication protocol MODBUS RTU. Easy mounting of the converters is ensured by the unique “S head” design invented by SENSIT s.r.o.

The converters are designed to be operated in a chemically non-aggressive environment. The converters are made in variant:

  • ST 485C – the command structure corresponds with the ModBus RTU communication protocol.


  • EU Declaration of Conformity – in accordance with Act 22/1997 Coll. on technical requirements on products as amended.
  • 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
  • Dimensional draft
  • Přiložené soubory
Converter type ST 485C
STD 485C
Input signal Pt 1000/3850
Power supply 10 to 35 V DC(unstabilized) 14 to 24 V AC
Power consumption max. 1000mW
Measuring range -50 °C to 150 °C
Communication properties communication via RS 485 maximum segment length is 1200 m, asynchronous transfer
preset transfer speed 9600 Bd optional transfer speeds 1200, 2400, 4800, 9600, 19200, 57600, 115200 Bd - DIP switch
247 modules / 1 serial port
protocol ModBus RTU 1 stop bit, without parity
Accuracy of electronics 0.05 %
Accuracy of sensing element ± 0.5 °C
Resolution 0.01 °C
Ingress protection IP 65 in accordance with EN 60 529
Recommended wire cross section 0.14 to 1.5 mm^2
Material of the sensor stem stainless steel DIN 1.4301
Material of the connection head POLYAMIDE
Operating conditions ambient temperature: -30 °C to 70 °C
relative humidity: max. 85% (at the ambient temperature 25 °C)
atmoshperic pressure: 87 to 107 kPa
Weight 0.2 kg

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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