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# mMPXV7002DP Airspeed measurement

Question asked by Nadi Abu Mahfouz on Jan 31, 2019

Hello,

I'm using mMPXV7002DP and I'm trying to convert the output to measure airspeed. I'm not sure I'm converting the voltage to pressure in a right way or not. based on the data sheet the minimum output voltage is 0.5 equal -2kPa and the maximum is 4.5 equal 2kPa. so based on this I have this equation

pressure = ((voltage - Vmin) * (Pmax- Pmin) / (Vmax- Vmin)) + Pmin

Vmin = 0.5

Vmax = 4.5

Pmin = -2

Pmax = 2

I have 3.3V refrence and 14bit ADC and I'm converting the ADC to Voltage

voltage = (((ADC * 3.3) / 2^14)) - 2.5;

the "- 2.5" based on the datasheet is the offset value of the sensor.

my last step, I'm calculating the Airspeed,

pressure = 0.5 x density x velocity x velocity
density  = 1.225kg/m3 for sea level air density.

my problem is I'm not sure am I calculating everything in a right way or am I missing something? because I'm trying to measure inside a closed room also the room has AC and I'm getting negative pressure all time.

Thanks,

Nadi