ASTM D149 Dielectric Strength
ASTM D149 Dielectric Strength 2

ASTM D149 is a method of measuring the dielectric strength of insulating materials using AC.

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Purpose: Measures the amount of AC voltage that an insulator can withstand before it burns through.

Sample: Seven (7) panels, 4 x 4 x 0.125 inches or larger.
Smaller samples can sometimes be tested.

Price & Delivery: Contact us for a quote.

Basic Description: Metal electrodes are placed on the top and bottom of a panel. AC Voltage is applied to the electrodes at a frequency of 60 Hz and the voltage is slowly increased until it burns through the center of the panel. The voltage is divided by the thickness of the panel to get dielectric strength in volts/mil. One mil is equal to 0.001 inches. Five panels are tested and the five results are averaged. Samples can be tested while surrounded with air or oil. Oil helps to prevent the voltage from arcing through the air around the sides of the panel and instead forces it to burn through the sample.

Limitations: Our equipment has a capacity of 100,000 volts or when an electrical arc goes around the sample, whichever comes first. Dielectric constant is a different test method (ASTM D150) which measures the relative capacitance of an insulator and is often confused with dielectric strength because of the similar name.


  • Hipotronics Dielectric Strength Tester, Model 7100-5/D149, 100,000 VAC

Method Publisher:


  • Dielectric Strength
  • Breakdown Voltage
  • Hipot Tester
  • AC Voltage Resistance

Related Techniques: