Sensor device having plural resistance change sensors and method of using the same

An image forming device comprising:

• a sensor device;
• and
• an image forming portion configured to form an image on an object based on image data,
• wherein the sensor device includes:
• a first resistance change sensor having a first terminal and a second terminal and configured to detect a first parameter;
• a second resistance change sensor having a third terminal and a fourth terminal connected to the first terminal and configured to detect a second parameter different from the first parameter;
• a fixed resistor having a fifth terminal and a sixth terminal connected to both the first terminal and the fourth terminal;
• and
• a controller having a first output port connected to the second terminal, a second output port connected to the third terminal, a third output port connected to the fifth terminal, and an input port connected to all of the first terminal, the fourth terminal and the sixth terminal, the controller being configured to:
• execute a first signal applying process wherein the first output port is rendered high impedance, and an alternating voltage is applied across the second output port and the third output port where the alternating voltage alternately changes between a first voltage level and a second voltage level different from the first voltage level, the high impedance being high to substantially be equivalent to an open circuit,
• execute a first detection process wherein a first detection voltage applied to the input port is detected when the second output port is at one of the first voltage level and the second voltage level and the third output port is at remaining one of the first voltage level and the second voltage level during execution of the first signal applying process,
• execute a second signal applying process subsequent to the execution of the first detection process, wherein one of the second output port and the third output port is rendered the high impedance, the alternating voltage is applied across the first output port and remaining one of the second output port and the third output port,
• execute a second detection process subsequent to the execution of the first detection process, wherein a second detection voltage applied to the input port is detected when the first output port is at one of the first voltage level and the second voltage level and the second output port or third output port whichever is not rendered the high impedance is at remaining one of the first voltage level and the second voltage level during execution of the second signal applying process, and
• execute a parameter detection process wherein a value of the first parameter is determined using the first detection voltage and the second detection voltage.