7 steps for measuring DC with a multimeter
1. Carry out mechanical zero adjustment;
2. Select the appropriate range gear;
3. When using the multimeter current block to measure the current, the multimeter should be connected in series in the quilt test circuit, because only the series connection can make the current flowing through the ammeter the same as the current of the branch under test. When measuring, the branch under test should be disconnected. Connect the red and black test leads of the multimeter in series between the two disconnected points, and pay special attention to the fact that the ammeter cannot be connected in parallel in the quilt test circuit. Doing so is very dangerous, and it is easy to burn the multimeter;
4. Pay attention to the polarity of the measured electricity;
5. Correct use of scales and readings;
6. When the 2.5A range of DC current is selected, the red pen of the multimeter should be inserted into the 2.5A measurement jack, and the range switch can be placed on any range of the DC current range;
7. If the DC current measured by the quilt is greater than 2.5A, the 2.5A block can be extended to 5A block; the method is very simple, the user can connect a 0.24 ohm plug between the "2.5A" jack and the black test lead jack Resistor, so that the gear becomes a 5A current gear, the connected 0.24A resistor should be a wire-wound resistor of 2W or more, if the power is too small, it will burn out.
Multimeter composition structure
1. Pointer gauge
It is a high-sensitivity magnetoelectric DC ammeter, and the main performance indicators of the multimeter basically depend on the performance of the meter head. The sensitivity of the meter head refers to the DC current value flowing through the meter head when the pointer of the meter head is deflected at full scale. The smaller the value, the higher the sensitivity of the meter head. The greater the internal resistance when measuring voltage, the better its performance. There are four scale marks on the meter head, and their functions are as follows:
① (from top to bottom) is marked with R or Ω, which indicates the resistance value. When the switch is in the ohm block, read this scale line.
② Marked with ∽ and VA, indicating the AC, DC voltage and DC current value, when the transfer switch is in the AC, DC voltage or DC current position, and the range is in a position other than AC 10V, read this scale line.
③It is marked with 10V, which indicates the AC voltage value of 10V. When the switch is in the AC and DC voltage range and the range is AC 10V, read this scale line.
④ marked with dB, indicating the audio level.
2. Digital header
The head of a digital multimeter is generally composed of an A/D (analog/digital) conversion chip peripheral component liquid crystal display. The accuracy of the multimeter is affected by the head. 1/2 digit DMM, 4 1/2 digit DMM, etc. Commonly used chips are ICL7106 (3.5-digit LCD manual range classic chip, subsequent versions are 7106A, 7106B, 7206, 7240, etc.), ICL7129 (4 and a half LCD manual range classic chip), ICL7107 (3.5-digit LED manual range classic chip).
