The power box in the substation and the AC and DC power supply in the terminal box are not clearly marked during construction. Many of the markings are not clear due to the long-term identification. If blind access to electrical equipment occurs, an accident will occur. We have made a lot of mistakes here to connect the welding machine and voltage regulator to the DC power supply, causing equipment burning accidents. Now based on work experience, the lesser method of determining the delivery, DC power supply, for beginners reference.
1. Use a stylus to determine if the neon tube only emits light at one pole, then the measured power source is DC, and the measured power is positive when the pole of one of the metal heads of the pencil (ie, the one near the hand touches) is bright. Electricity, on the contrary, negative electricity.
2. Use a mechanical multimeter to judge, put the multimeter separately, DC voltage file test. If there is a reading when in the AC position and there is no reading in the DC position, the measured power supply is AC. If the readings measured in the two positions are similar, the measured power supply is DC.
3. Judging with a digital multimeter, test the multimeter with AC and DC voltage files respectively. If the reading is from the AC position and there is no reading at the DC position, the measured power is AC. Otherwise, it is DC. If the direct current is impure, DCTV will also have readings in the AC range. However, the value is generally small and it is actually the AC component contained in the DC.