You can perform a DC withstanding voltage tests using TOS9301,TOS9301PD, TOS9303, TOS9303LC, or TOS9311. To perform the test: 1. Press the Menu key or the HOME/FUNC key to open the Function Menu. 2. Select DCW. 3. Set the test voltage. 4. Perform the test. For more details, read the user’s manual – chapter of Withstanding Voltage and Insulation Resistance Tests – Setting Test Conditions.