1) The following circuit has Rse as the Mass airflow rate sensing element where
ID: 2291335 • Letter: 1
Question
1) The following circuit has Rse as the Mass airflow rate sensing element where the bridge is balanced at the reference temperature of the sensor which is 100 Deg C The MAF sensor has a Resistance/Temperature Coefficient of -1 Ohms/1 Deg C and a 0.0325 Kg/Sec air flow rate for every 1 ohm change in the Rse value The A2D port of the microcontroller is an 8-bit Port (this means that any analog input voltage will be digitally represented by an 8-bit binary number anywhere between 0 counts and 255 counts for 0 and 5 Volts respectively) a) b) c) d) e) f) What resistance value would the MAF sensor would have at the reference temperature? What is the gain of the difference amplifier? What is the value of VAB at 400 Deg C? What is the value of Vout at 400 Deg C? What digital value would the A2D port read at 400 Deg C? If the A2D digital read is 25 counts, then what is the mass air flow rate indicated by the sensor? Rf R3 500? R1 Ri V1 12V Vout Vout Rin1 A2D0 Rin2 R2 se Micro ControllerExplanation / Answer
a) under balavced condition
R1.Rse=R2R3
Rse=4K.500/1k=2k ohms
temperature coefficient of resistance =1 ohm/1 deg C
Rse at the referance temperature 100 deg C=200k ohms
b)gain of diff amplifier
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