A measurement is started by pressin

A measurement is started by pressing the Measure button on the Home screen (Figure 2). The Measure button is not activated unless the CAT is connected to the computer. The lights in the top right hand side of the screen (Figure 6) indicate whether the CAT is connected and if a test is in progress.During a run the Measure screen appears as in Figure 6. The speed indicator in the middle of the screen is green if you are within +/-20% of the desirable speed for taking a measurement: this is 1m/s for 2mm spacing (used for corrugation measurements) or 0.5m/s for 1mm spacing (typically used for acoustic roughness measurements). The speed indicator is red if you are outside this range. The display is provided simply to give the operator confidence that a measurement is being made: the operator should not attempt to assess whether rail is corrugated by looking at the online display (Figure 6).