The DC resistance tester is mainly used to test the DC resistance of switch contacts, circuit breaker contacts, bus bars, contacts, SF6 switches, various connections, fuses and railway connections.

Working principle: A thyristor rectifier circuit is used to adjust the predetermined value of the test current. After rectification and filtering, the current is applied to the sample under test, and the resistance value is directly measured. In this current, the voltage is applied to an unknown circuit under test and a circuit with a known resistance value for comparison, and the reading is displayed on the digital ammeter. The test principle adopts the four-terminal test method. The four-terminal connection method is used for the unknown resistance to be tested and its parallel circuit. The test circuit and its selector switch determine the test range.

Precautions:

1. For no-load voltage regulating windings, it is not allowed to switch the no-load tap changer during the test or when the power is not fully discharged.

2. For the inductive resistance test object, it is not allowed to remove the test wire when the power is not discharged (when the buzzer is sounding) to avoid electric shock.

3. When the external AC220V is suddenly cut off during the test, the instrument will start to discharge automatically. At this time, it is not allowed to remove the test wire immediately, and the wire can be disconnected after 5 minutes.

Security measures:

1. Read this manual carefully before using the transformer DC resistance tester.

2. The operator of the transformer DC resistance tester should have general electrical knowledge.

3. Use the instrument to avoid places such as rain, corrosive gas, excessive dust, high temperature, and direct sunlight.

4. The meter should avoid violent vibration.

5. After the test is completed, be sure to wait for the discharge alarm to stop before turning off the power, and remove the test line.

6. When measuring the no-load voltage-regulating transformer, you must wait for the discharge indication alarm sound to stop before switching gears.

7. During the test, it is forbidden to move the test clip and the power supply line.