The VBT-75 S2 is Vanguard's second generation microprocessor-based, portable, 75kV dc vacuum bottle tester. This lightweight, portable tester is designed for testing circuitbreaker vacuum bottles in the field and at the shop.

Test voltages can be selected from 10 kV dc to 75 kV dc in 5 kV steps. The high-voltage test time can be set from 5 seconds to 2 minutes. The test voltage is raised to the selected voltage and held for the test time duration. After the test time duration has elapsed and the leakage current did not pass the preset value of 100 μA, 200 μA, or 300 μA, the test voltage is returned to zero and a "Pass" message is displayed. If a flash-over condition occurs, such as bottle failure, the test voltage is immediately turned off, a “Failure” message is displayed on the LCD screen, and the “TEST FAIL” LED light on the unit is also illuminated.

The presence of high voltage is indicated by an audible tone and an illuminated “HIGH VOLTAGE” LED light. For additional operator safety, an “ARM” switch must be held down during testing.

The VBT-75 S2 features a back-lit LCD screen (20 characters by 4 lines) that is viewable in both bright sunlight and low-light levels. A turn-and-press knob is used to control the unit. The VBT-75 S2's firmware can be updated in the field via the unit's built-in USB Flash drive port.

The VBT-75 S2 is furnished with a 10-foot test cable that is terminated with a quickdisconnect test clip. A transportation case is also included.