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Temperature and Gas-Pressure Controllers  

Typically these control loops have slower dynamics than flow controllers and, unlike level controllers, cannot be tuned by calculation alone. An estimate of the process dynamics is needed in order to calculate the required tuning constants.

Because temperature-control can be quite slow, Derivative action may be useful. Some slow-responding pressure controllers can benefit from Derivative action, but usually they just require high gain and moderate integral action.

The most commonly used traditional method for tuning non-level controllers is to use the Ziegler-Nichols equations, developed in the United States in 1942. The equations are included here for reference and completeness. They should not normally be used as written, because the equations were developed in laboratory conditions for 'quarter amplitude decay'. In real life this is too aggressive for most process control loops; the control valve is likely to be moved violently, which can cause upsets elsewhere in the process. The best tuning method available is the ITAE method.