How to preserve the position of the encoder after rotary encoder without electricity?

If incremental encoder after the power system, the encoder by artificial action, then after startup, measurement error will occur. So, how to after the power system, can still be memory pulse encoder issued? The best way is to use the absolute value encoder. Normal, incremental encoder, when the power is what can't be found guilty of a pulse, but we can through the startup, when the power is automatically back to the origin to determine the pulse encoder. So, absolute value encoder rotation, when the power is back on after the electricity location value will change? Absolute value encoder 'code value measured' position 'with corresponding is the only, have' power off memory function, no rotation measurement error accumulation, in 'a loop is used to measure and control field than the incremental encoder is superior, the additive before reducer adjustment range. Widely used in home appliances, automotive, instrumentation and other industries. Called absolute encoder, because every place has a duplicate is not absolute value. With or without electricity, as long as at a certain position, is a certain value. Electricity can put this value output. Say you stop position is 512, to 1024, when the power is to continue to electricity, it can tell you, right now the position is 1024. Incremental encoder can only record the change of value, to power after the change can't identify. Only in the case of a power supply, to tell you, how much increase, or decrease how much.