The sensor may be connected directly to an NXT sensor port or via the HiTechnic Sensor Multiplexer (MUX). When configuring the sensor via the multiplexer, there are two port selections to make. The first is the NXT to MUX connection and the second, the MUX to SENSOR connection.

 

The Magnetic Reading output indicates the relative strength of the magnetic field measured. When the sensor is not in the proximity of a magnetic field, the output should be zero. Due to manufacturing tolerances, temperature and other effects, the output may be a small positive or negative number. To cancel out this zero offset error, also referred to as bias, an offset input can be applied.

 

Offsetting bias

 

The simplest way to measure and offset the bias, is to keep the sensor away from magnetic fields and read the output with the Offset value set to zero. This value can then be used in the future as the Offset value which will then cause the output value to be zero when no magnetic field is present.

 

Other Programming Environments

 

RobotC

 

All features of the HiTechnic Magnetic Sensor can be accessed using RobotC. The RobotC drivers pack that is available on this downloads page will include drivers for this sensor.

 

NXC

 

NXC is a C like programming language that can access all the features of this sensor. 

For more information go to http://bricxcc.sourceforge.net/nbc/.

 

Example NXC Code

 

// The Magnet sensor has the same interface as the Gyro Sensor.
// These are temporary macros until native functions are available
// in the official NXC release.
#define SensorHTMagnet(port,offset) SensorHTGyro(port,offset)
#define SetSensorHTMagnet(port)       SetSensorHTGyro(port)

#define MAGNET   IN_1

task main()
{
  int offset, magnetic_value;
  
  SetSensorHTMagnet(MAGNET);

  TextOut(0, LCD_LINE1, "HiTechnic");
  TextOut(0, LCD_LINE2, " Magnetic Sensor");

  TextOut(0, LCD_LINE4, "Calibrating, ");
  TextOut(0, LCD_LINE5, "keep magnets");
  TextOut(0, LCD_LINE6, "away...");
  Wait(1000);
  //Get inital offset assuming no magnetic field is present.
  offset = SensorHTMagnet(MAGNET, 0);
  TextOut(0, LCD_LINE4, "     Value:      ");
  TextOut(0, LCD_LINE5, "                 ");
  TextOut(0, LCD_LINE6, "                 ");

  while(true) {
    magnetic_value = SensorHTMagnet(MAGNET, offset);
    
    TextOut(6*7, LCD_LINE5, "     ");
    NumOut(6*7,LCD_LINE5, magnetic_value);

    Wait(100);
  }
}

Downloads;