Investigation on new sensors for a contactless impulse voltage measurement

Dividers used for the impulse measurement are usually large and expensive equipment. They also add capacitive load, which reduces the impulse generators efficiency. Because of the high field strength, the impulse can also be recorded with a field sensor and an oscilloscope. The impulse measurement with a field sensor could be an alternative or at least an addition to standard dividers. Especially, since battery operated oscilloscopes with wireless communication allow a field sensor to be placed virtually anywhere in the test facility. The RedPitaya (RP) is an affordable experimental board with two DACs with 125 Msamples/s and 14 bit resolution. It can be battery operated and remote controlled via WLAN. The RP is used with different field sensors to record lighting and switching impulses. These are compared to the measurements with a voltage divider and transient recorder. The tests are performed at the Schering-Institute of the University of Hannover and at the National Metrology Institute of Germany Physikalisch-Technische Bundesanstalt (PTB). It is shown, that field probes can be used to accurately measure the peak voltage, but the wave shape, especially the time to half-value, depends on the field sensor performance. This can be corrected with digital signal processing. If calibrated correctly, field sensors can be a valuable addition to impulse voltage test systems.