The Ultrasonic Contact Impedance (UCI) method uses a Vickers diamond indenter, allowing for precise placement and resulting in a highly localized hardness test. But unlike in conventional Vickers testing, the reading is not derived through optical measurement of the test indentation. Instead, the indentation area is detected by electronically measuring the shift in an ultrasonic frequency that occurs when the load is applied. This approach to hardness testing is standardized by ASTM A1038. It is intended not to replace traditional Vickers testing, but rather to complement it with a quick, field portable test method.