The DC resistance test is to check the welding quality of the windings and whether the windings have short circuits between turns; check whether the winding conductors or lead wires have broken bones or open circuit faults, check whether there are short circuits between turns and layers, and whether the contacts of the tap switch are good And whether the actual position of the tap changer matches the indicated position.

 experiment procedure

1. Use the power cord to connect the instrument to an external AC220V power supply (the instrument with a battery may not be connected to the external power supply), the +I, -I, +V, -V terminals are connected to the test product by four-terminal wiring, the test line and test Clamp, thick wire is connected to current I, thin wire is connected to voltage V;

2. Connect the ground wire at the same time. When testing, you can choose automatic testing or select the appropriate current according to the approximate resistance of the sample;

3. Turn on the power switch and press the "Select" button to select the output current. After the current is selected, press the "Confirm" button. The instrument will perform the test. After the resistance value is displayed, press this button for 1-2 seconds to retest and speed up the data stability. After the measurement data is displayed, press the "Select" key for 1-2 seconds to print the resistance value.

Precautions

1. When connecting the test clip and the ground wire, pay attention to the contact end being exposed to the air for a long time, and the surface is covered with an oxide film. The oxide film may cause unstable or inaccurate measurement results, so pay attention to cleaning up the oxidation when wiring After the film or the test clip is connected to the terminal, twist the test clip several times to break the oxide film to ensure a good connection;

2. It must be reset before testing the reverse tapping of the no-load voltage regulating transformer. After the discharge is over, the alarm sound will stop for more than 10 seconds before the tapping point can be switched;

3. Before removing the wire, be sure to wait for the alarm to stop after the discharge is over. Try to wait for more than 10 seconds to turn off the power before removing the wire to ensure that the charge is completely released;

4. When selecting current, please refer to the range in the technical index column, and do not use over range or under range. When the range is exceeded, the instrument is always in the "charging" state because the current does not reach the preset value. When these two states appear, confirm the range and select the appropriate output current for testing.