Dwyer Instruments, Inc. manufactures and offers many temperature measuring products that use a thermistor as the sensing element.
Thermistors are based on the principal that the electrical resistance of semiconductor materials is a function of the temperature. Thermistors work well over smaller temperature ranges with better accuracy than (RTD) but are very non-linear. They also generally offer better response times. Thermistors have much higher resistance values than RTDs, with ranges typically ranging from 100 ohms to 100 megaohms.
The velocity of an air stream in a duct is not uniform over the cross section of the duct. This is because friction against duct walls causes the air velocity to be lower near the sides than the velocity in the center, creating a parabolic velocity profile. 
Many Dwyer Instruments, Inc. products sense and measure 
Pressure is the amount of force acting on a specific area and is equal to the force divided by the area.