5.2 Pressure Sensor Interface with Differential Output Voltage Using PIC16F17146 Microcontroller
The MEMS gauge pressure sensor 2SMPP-02 from Omron is capable of measuring air pressure till 37 Kpa and gives differential output in the range of 0 to 31 mV. This sensor requires a constant current of 100 µA for excitation.
Figure 5-2 shows a block diagram view of the necessary connections while interfacing pressure sensor to the PIC16F17146 microcontroller.
OPA: Configured as gain stage for the signal provided at positive input channel of the differential ADCC.
DAC: Configured to provide constant current of 100 µA.
ADCC: The Differential mode of ADCC is used to interface the sensor’s differential output signal. The ADCC also measures the excitation current of the sensor by measuring voltage across a resistor connected between the sensor pin ICC and circuit ground. This way, a constant current of 100 µA can be maintained by implementing a feedback loop. The current can be modified by adjusting the DAC output value.
FVR: Provides stable voltage reference to the ADCC.