 The choice of method will depend largely on whether or not the loop can be taken offline for tuning, and on the response time of the system.If the system can be taken offline, the best tuning method often involves subjecting the system to a step change in input, measuring the output as a function of time, and using this response to determine the control parameters.If the system must remain online, one tuning method is to first set formula_38 and formula_39 values to zero.