Position sensitive detector（PSD）

which has several excellent performances—short response time

high position resolution and large response range of spectrum

is a new type of position sensitive detecting devices.The structure and the operational principle of the PSD are introduced.The expressions of the function of position coordinate and the block diagram of relevant output signal detection circuit are given.The application of PSD in measurement of shafts elevation changes on steam-turbine generator sets is investigated.Not only the factors affecting measurement accuracy are analyzed

but also the solving method is proposed.And an example of detecting elevation is provided.The test results indicate that the elevation measurement system based on 2D PSD is stable and its detecting data is reliable.