The aim of this study is to develop an automatic control loop monitoring system. The first step includes the detection of changes and of oscillations in the control error and in the control signal. To determine the test parameters of the statistical change detection test (a CUSUM test), the average run length (ARL) function is exploited. To detect oscillations, a modified version of Hägglund’s approach is presented. Methods are proposed in order to help the operator in the choice of the parameters for both detection tests. The second step should consist in determining the origin of the oscillations or of the changes. Only the first step is presented in this work.