* The BNC shield is at earth ground. Use only the probe TIP for measuring high voltages. "Floating" the BNC shield or connecting it to a high voltage could cause a safety hazard. * Make sure probes are compensated and set to proper scale (X1,X10,X100). * If you can't get the signal on screen: - Check Probe connection - Touch: SETUP, Default Setup - Touch: AUTOSCALE - Check for offset (ground symbol). If offscale, adjust vertical sensitivity. If still offscale, Touch: - Check Trigger Source - Set Mode Auto