We has developed DST Insulating Oil Dielectric Strength Tester according to International standard IEC156, which is developed especially for measurement of insulating oil breakdown voltage. The dielectric breakdown is an indication of the oil ability to withstand electrical stress. The oil sample is placed in a test cup and an AC voltage is impressed on it. The electrodes are two discs, exactly 1 in. in diameter and placed 0.10 in. apart. The voltage is raised at a constant rate, until an arc jumps through the oil between the two electrodes. The voltage at which the arc occurs is considered the dielectric strength of the oil. DST automatic Insulating Oil Dielectric Strength Tester is unique in the market due to its functionality and the excellent user benefit in comparison to costs. The transformer oil tester provides delivers clear and reliable measurement results. It is no longer necessary to send samples to the laboratory. Environmental and transport influence on the samples are minimized. Due to its design, the tester is particularly handy, easy to operate and especially excellent to use under tough ambient conditions. By proper programming, DST Insulating Oil Dielectric Strength Tester has got functions of auto boosting, step down, stirring, display and print out. Portable type is available for performing both levels of this test in the field.