How to use a multimeter to check circuit lines
Multimeter, also known as multiplex meter, multimeter, three-purpose meter, multimeter, etc., is an indispensable measuring instrument in power electronics and other departments. It is generally used to measure voltage, current and resistance as its main purpose. Multimeters are divided into analog multimeters and digital multimeters according to their display modes. It is a multi-functional, multi-range measuring instrument. Generally, a multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level. Some can also measure AC current, capacitance, inductance and semiconductor. Some parameters (such as β), etc.
How to use a multimeter to check circuit lines
When the power is on, use the AC voltage level or the DC voltage level depending on the situation! Use electrical barriers to detect circuit paths and shorts without dots!
The multimeter has a buzzer, which is to use two test leads to test the same wire. If there is a short circuit, there will be no response. If it is a path, there will be a buzzing sound. Sometimes when the device itself is electrified due to poor grounding, you can use the red test lead of the multimeter to place it on the black mark on the shell. Rather than directly contacting the ground, the electrical strength of the leakage of the shell can be measured so that the electrical appliance can be informed of the rest of the work. It can also be connected in series to the circuit to measure the AC and DC current.
To check whether the circuit is leaking, you must use a megohmmeter (micrometer), because the voltage of the multimeter is low (9v) and the voltage of the megohmmeter is higher, 500v. Because the line working voltage is 220v, it is difficult to diagnose lines with no obvious leakage. If you want to use a digital meter to check line leakage, you first need to cut off the power supply. After discharging the line, use the resistance level and 2M level to measure. The normal display is 1 (infinity).
To measure whether the circuit is connected, you can use the ohm range of a multimeter to measure it. When measuring, select the meter pointer to deflect 0 ohms. If the line is in the circuit, one end of the line (end A) should be connected to the 100 ohm level of the multimeter (red test lead), and the black test lead should be connected to the other end of the line to be measured (end B). If the measured result is zero, it means this A connected line is also called a path. Only through a path can current flow through the circuit. If the pointer of the multimeter ohm meter from end A to end B of the line is not close to zero ohms, the line is already in an open circuit state. Disconnection is called Break or open circuit.
How to use a multimeter to find problems
When checking electrical faults, a multimeter generally uses only two settings, one is the voltage range (including AC and DC voltage ranges) and the other is ohms.
If the equipment stops working, your first thought is whether the voltage of the equipment is normal. You need to use the voltage range of the multimeter (select AC voltage range or DC voltage range, depending on whether your device is AC equipment or DC equipment) to measure. If the control loop or secondary circuit is disconnected, if you are familiar with the schematic diagram, you must also use the voltage range to measure whether the voltage at a certain place is normal. If it is determined that the voltage at that place should not be there, it is there, and it is not there when it should be. , it means there is a disconnection or poor contact there. In order to be more sure whether there is a problem there, you have to disconnect the power supply of the equipment at this time, and use the ohm range of the multimeter to confirm whether the connection is indeed broken in order to troubleshoot. Roughly speaking, it mainly depends on your familiarity with the equipment and the accumulation of experience at work.
