Delta Ohm HD402 Low Pressure Transmitters

The HD402… series is composed of pressure transmitters and pressure ON/OFF relay switches. The instruments measure relative pressure with respect to atmosphere or differential pressure in the range from 50 Pa to 200 kPa (depending on model) by using a silicon piezoresistive sensor with high accuracy and temperature compensation, which allows excellent linearity, repeatability and stability over the time.

Thanks to the particular sensor used, the instruments are insensitive to the mounting orientation and position. Moreover, the high stability of the sensor over the time and in comparison to the changes in temperature allows eliminating the operations of maintenance typically required to compensate for the aging and the deviation of the sensor zero. The auto-zeroing feature in the HD402TR1L low range model allows stable measurements over the time without the need to recalibrate.

Available outputs, depending on the model:

• RS485 Modbus–RTU digital output (HD402ST…);
• 0...10 V voltage analog output (HD402T…);
• 0...20 mA / 4...20 mA active current analog output (HD402T…);
• 2-wire (current loop) 4...20 mA analog output (HD402AT…);
• ON/OFF relay switch (HD402TR…L).

Different units of measurement can be chosen for each model and, in the models with analog output, it is possible to choose the full scale (f.s.) value for the output (high, intermediate or low range) and set the unipolar (0...+f.s.) or bipolar (-f.s....+f.s.) measuring range.

Versions with optional 4-digit LCD display (option L) are available, which allow the measured parameters to be displayed. The pressure relay switches always include the display.

The configuration can be made by connecting the serial port of the instrument to the PC or by means of the quick configuration dip switches on the circuit board. The versions with relay switch output are equipped with two internal buttons for the configuration via display.

The instruments are factory calibrated and ready for use