What are the precautions for using DC ammeter

What are the precautions for using DC ammeter

                       
Update:2021-11-04
Summary:Precautions for the use of DC ammeter1. The ammeter should be connected in series in the circuit.2. ...
Precautions for the use of DC ammeter
1. The ammeter should be connected in series in the circuit.
2. Choose the appropriate range according to the measured current. For an ammeter with two ranges, it has three terminals. When using it, you must see the terminal range mark, and connect the common terminal and a range terminal in series in the circuit under test.
3. When measuring DC current, the polarity of "+" and "-" on the terminals of the DC ammeter must not be connected wrongly, otherwise the meter may be damaged. Magnetoelectric ammeters are generally only used to measure direct current.
4. It is absolutely not allowed to connect the ammeter directly to the two poles of the power supply without using electrical appliances.
5. The measured current should not exceed the range of the ammeter.
6. Select the appropriate accuracy to meet the needs of the measurement. The ammeter has internal resistance. The smaller the internal resistance, the closer the measurement result is to the actual value. In order to improve the accuracy of the measurement, an ammeter with a smaller internal resistance should be used as much as possible.
7. The positive and negative terminals of the ammeter must be connected correctly, so that the current flows from the positive terminal into the ammeter and flows out from the negative terminal.
8. Choose the appropriate accuracy to meet the needs of being measured. The ammeter has internal resistance. The smaller the internal resistance, the closer the measurement result is to the actual value. In order to improve the accuracy of the measurement, an ammeter with a smaller internal resistance should be used as much as possible.
How to use DC ammeter
Before using the DC ammeter, check whether the pointer is aligned with the zero point. If there is any deviation, you need to adjust the pointer to the zero position with a zero-point adjuster. When adjusting, you only need to turn the zero-point adjustment knob in the middle of the front of the meter cover.
Rules for the use of ammeter:
(1) Be sure to connect the ammeter in series with the circuit under test.
(2) When measuring DC current, the polarity of "+" and "-" on the terminals of the DC ammeter should not be connected wrongly, otherwise the meter may be damaged. Magnetoelectric ammeters are generally only used to measure direct current.
(3) The appropriate range should be selected according to the size of the current to be measured. For an ammeter with two ranges, it has three terminals. When using it, you must see the terminal range mark, and connect the common terminal and a range terminal in series in the circuit under test.
(4) Choose the appropriate accuracy to meet the needs of the measured. The ammeter has internal resistance. The smaller the internal resistance, the closer the measurement result is to the actual value. In order to improve the accuracy of the measurement, an ammeter with a smaller internal resistance should be used as much as possible.
(5) When measuring AC currents with large values, current transformers are often used to expand the range of AC ammeters.
The rated current of the secondary coil of the current transformer is generally designed to be 5 amperes, and the range of the AC ammeter used with it should also be 5 amperes. The indicated value of the ammeter is multiplied by the conversion ratio of the current transformer, which is the value of the actual current measured.
When using a current transformer, the secondary coil and iron core of the transformer should be grounded reliably, and no fuse should be installed at one end of the secondary coil, and it is strictly forbidden to open the circuit during use.