The present invention relates to a method for visualizing ST data based on principal component analysis. The blood analyzer includes a system for obtaining a first white blood cell number and a system for obtaining a second white blood cell number. The data can then be analyzed by the controller or other computer to vary the well’s operating parameters to maximize the well’s operating efficiency and the data can be used in reservoir management, such as transient testing, reservoir modeling and interference testing. Direct attachment minimizes the air gap between the latching magnet and a reed thus enabling latching with only an extremely small magnet.