HD404T / HD404ST Series – Low Pressure Transmitters

HD404T / HD404ST Series – Low Pressure Transmitters

Very low pressure relative or differential pressure, Low range 50 Pa, 4-20 mA or 0-10 Vdc

The series of HD404T transmitters is able to measure relative pressures with reference to the atmosphere or differential in the range:

  • from 50 to 1000 Pa (from 0.2” H2O to 4” H2O) for the versions with analog output;
  • 250 Pa / 1000 Pa / 100 mbar for the versions with RS485 Modbus‑RTU output.

The series uses a silicon “micro‑machined” type sensor compensated in temperature that has an excellent linearity, repeatability and stability over time. The output signal from the sensor is amplified and converted, depending on the model, into a standard current analog output (4-20 mA) and a voltage analog output (0-10 V), or into a digital RS485 Modbus‑RTU output, which, then, can be transmitted over long distances with a high immunity to noise.

In the models with analog output it is possible to choose, via a dip switch, between two measurement ranges in order to select the optimal scale for each application.

Typical applications for HD404… series are:

Clean room monitoring
Filter control
Flow measuring
Air conditioning control
Ventilation control

Usually the low pressure transmitters are susceptible to the guidance by which they are mounted. In HD404T series there is available a special auto-zero circuit, which periodically equalize the differential pressure at the input sensor and corrects the offset; the transmitters, provided with this circuit, are insensitive to the mounting position. In addition, the circuit compensates auto‑zero aging and the deviation of the zero of the sensor to temperature changes: virtually eliminates maintenance.
It’s available the (L) “display” option, in which the pressure is visualized on a display with 4 digits in the selected measurement unit.

The (SR) “square root” is especially useful if the transmitter is connected to a pitot tube, as the output is directly proportional to the speed of airflow.

The transmitters are ready to use and are supplied calibrated by the manufacturer.

Supplied with 1 piece of silicone tubing Ø 5 int./ Ø 8 ext. length 2 m and 2 plastic fittings (HD434T.5).

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