How is a Cd derived using a wind tunnel ?

[Cd]

How is Cd derived using a wind tunnel ? What type of sensors are used ?

Wind tunnel - Wikipedia, the free encyclopedia

I read over the Wikipedia article, but i didn't see anything specific.

I'm assuming it has to do with something called a 'force balance', since it says this can be used to find the Cd.

[NeilBlanchard]

The have the model linked to a strain gauge that can measure the drag and directly feed the value into a computer. Strain gauges are also used for solid state (read digital) weight scales.

[aerohead]

From the drag force equation,knowing the frontal area of the test model or vehicle, the local air density,air velocity/Reynolds number in the tunnel,any buoancy or wall correction factors of the tunnel itself,and the actual drag force measured with the scales,sting,or load cells,the coefficient of aerodynamic drag falls out of the equation.