Tester indicating voltage magnitude, polarity and testing continuity - has mains section and switchable reservoir enabling self-testing

摘要

The unit provides safe operating characteristics, positive indication and is practical to use. A switching mains section (A1) increases the battery voltage and is supplied by an oscillator. The mains section output is stored by an energy reservoir (A2) whilst a switching element (52) is held in its normal state. The element can be changed over to apply the stored charge to an isolation amplifier to enable automatic testing of the tester display functions. The test current is applied to the amplifier via current reducing series resistors. The amplifier drives the optical displays, which cover voltage ranges, and the polarity indicator.