Automatic control and display in impulse testing

Routine impulse testing is usually carried out using an impulse generator and a cathode-ray oscillograph, the breakdown of the object under test being indicated by the sudden collapse of the wave to zero. The method is limited by the difficulty of visual observation of the cathode-ray tube and by the time delay before the oscillogram may be measured. Many types of test would be facilitated by the employment of devices to display the peak voltage and duration of the impulse wave without delay, so that the limitations of the cathode-ray oscillograph could be overcome. The paper discusses circuits which enable an impulse generator to be triggered automatically at a preset charging voltage and allow the peak voltage and duration of the wave to be displayed on ordinary meters. In addition, the peak voltage of the wave applied to an object under test can be made visible to several observers without delay and an indication of the breakdown of the object under test can be presented. The circuits also permit automatic control of the test sequence to be achieved if desired. These circuits are not intended necessarily to replace the cathode-ray oscillograph but to augment it, so that routine testing may be facilitated. One of these circuits has been in operation for many months and has been found to be very reliable.