Editing Proportional–integral–derivative controller (section)

===Noise in derivative term===
A problem with the derivative term is that it amplifies higher frequency measurement or process [[noise]] that can cause large amounts of change in the output. It is often helpful to filter the measurements with a [[low-pass filter]] in order to remove higher-frequency noise components. As low-pass filtering and derivative control can cancel each other out, the amount of filtering is limited. Therefore, low noise instrumentation can be important. A nonlinear [[median filter]] may be used, which improves the filtering efficiency and practical performance.<ref>[http://eprints.gla.ac.uk/3815/1/IEEE_CS_PID_01580152.pdf Li, Y. and Ang, K.H. and Chong, G.C.Y. (2006) PID control system analysis and design - Problems, remedies, and future directions]. IEEE Control Systems Magazine, 26 (1). pp. 32-41. {{ISSN|0272-1708}}</ref> In some cases, the differential band can be turned off with little loss of control. This is equivalent to using the PID controller as a [[#PI controller|PI controller]].