In the instrument PID diagram, ns refers to NegativeStep, which means negative jump input signal. The full name of NS in Chinese is "negative step signal", which is usually used for the test and analysis of control systems. Pronounced as "NegativeStep", it can be directly translated as "negative step".

Instrument PID diagram is a graphical method to express the transfer function and control strategy of control system, and it is a common tool in the field of automatic control.