The Haefely line of sphere gaps or multiple chopping gaps can be used for either AC or DC voltage calibration (according to IEC 60052), as a load capacitor, or to provide a chopped lightning impulse. Chopping gaps are an important part of a complete Impulse Voltage Test System when a chopped impulse is required. Haefely offers two lines of chopping gaps, the MAFS series which is an automated multiple chopping gap and the KFS series which is a horizontal or vertical sphere gap. Integrated with Haefely control units GC 223 and GC 257 the sphere distances can be automatically adjusted on the vertical versions. This saves time in setup and also helps to provide a reproducible chopping time.