OK if it's puzzle time...

You have 10 piles of coins each pile appears to have 10 silver dollars in it, however 1 pile contains only counterfeit coins. You are given the weight of a real silver Dollar and the weight of a counterfeit dollar plus a pair of accurate digital scales.

You may weigh the coins in any order or quantity you choose, the object is to find the counterfeit pile in as few weighing operations as possible.

What is the minimum number of weighings?