Make sure that the test leads are removed from the instrument before making current measurements with the clamp ammeter
The clamp ammeter is a kind of instrument used to measure the current of the running electrical circuit. It can directly measure the working current of the running equipment without disconnecting the power supply and the circuit. In addition, it can also measure AC and DC voltage, resistance and pass the test.
There are many types of clamp ammeters, but their shapes are basically similar, as shown in Figure 9-13. Its usage is as follows:
(1) Matters needing attention when using clamp ammeter
①Estimate the size of the preliminary measured current before measurement, and select the appropriate range.
② When measuring, the current-carrying wire to be tested should be placed in the center of the jaws to avoid errors. For the measurement of the wire with less current, in order to improve the accuracy, if the conditions permit, you can also wind the wire under test several times, and then put it into the jaw for measurement. The actual current value is equal to the reading of the meter divided by the number of wire coils.
③ If there is noise during the measurement, it means that the jaws are not in good contact with the wires. You can open and close the jaws again. If the noise still exists, you can use gasoline to clean the jaws before measuring.
(2) Measurement operation method
① AC power measurement. Turn the switch to ACA1000A gear. Leave the switch in the relaxed position. Press the trigger to open the jaws, grip a wire, and read the value. If the reading is less than 200A, turn the switch to ACA200A to improve the accuracy of the reading.
② AC and DC voltage measurement. When measuring DC voltage, turn the switch to DCV1000; when measuring AC voltage, turn the switch to ACV750V, and keep the switch in a relaxed state. Connect the red test lead to the "VΩ" terminal, the black test lead to the "COM" terminal, then connect the red and black test leads to the circuit under test in parallel, and the read value is the actual voltage of the circuit.
③Measurement of resistance. Turn the switch to the electric resistance of the appropriate range. Leave the switch in the relaxed position. The red test lead is connected to the "VΩ" terminal, and the black test lead is connected to the "COM" terminal. Connect the red and black test leads to both ends of the measured resistance, and the read value is the actual resistance value of the measured resistance.
Note: When measuring online resistance, the line should be powered off and the capacitor connected to the resistor should be discharged.
④Continuity test. Turn the switch to 200Ω, connect the red test lead to the "VΩ" terminal, and the black test lead to the "COM" terminal. If the buzzer in the meter sounds, it means that the resistance between the red and black test leads is less than 50±2.5Ω.
How to use the clamp ammeter correctly? What should be paid attention to when using it?
How to use clamp ammeter
1. Before measuring, check whether the rubber insulation of the clamp core is intact. The jaws should be clean and free from rust, with no obvious gaps after closing.
2. When measuring, you should first estimate the magnitude of the measured current and select an appropriate range. If it is impossible to estimate, you can choose a larger range first, and then reduce it step by step to switch to a suitable range. When changing the range gear, it must be done without power or with the jaws open to avoid damage to the meter.
3. When measuring, the wire to be tested should be placed in the middle of the jaw as much as possible. If there is any noise on the joint surface of the jaw, it should be opened and closed again. If there is still noise, the joint surface should be treated to make the reading accurate. Also, do not clamp two wires at the same time.
4. When measuring the current below 5A, in order to obtain a more accurate reading, when conditions permit, the wire can be wound a few more times and put into the jaw for measurement. The actual current value should be the meter reading divided by the wire put into the jaw. The number of.
5. Before and after each measurement, the switching switch for adjusting the current range should be placed at the highest position, so as to avoid damage to the instrument due to measuring without selecting the range next time.
Precautions
When measuring current with a clamp ammeter, be sure to clamp a wire (wire) under test. If two (parallel wires) are sandwiched, current cannot be detected.
In addition, when the center (core) of the clamp ammeter is used for detection, the detection error is small. When checking the power consumption of home appliances, it is more convenient to use a line splitter. Some line splitters can amplify the detection current by 10 times, so the current below 1A can be amplified before detection.
When detecting DC current (DCA) with a DC clamp ammeter, if the current flows in the opposite direction, it will display a negative number. This function can be used to detect whether the car's battery is charged or discharged.
