3 questions about using a multimeter to find lines
How to use a multimeter to find problems_How to use a multimeter to check lines_How to use a multimeter to check lines
1. When powered, measure the key points or power-saving voltage, and judge whether the circuit is normal based on the voltage level;
2. When charged, measure key points or power-saving current, and judge whether the circuit is normal based on the size of the current;
3. In the event of a power outage, measure the resistance of the circuit and components to determine whether the circuit is normal (short circuit, open circuit, etc.).
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. If you have any questions, please feel free to ask.
1. How a multimeter records intermittent faults:
Use the multimeter's min/max/average recording mode, select the corresponding power (AC voltage, DC voltage, resistance, AC current, DC current and frequency) according to the measurement item, and make sure to connect it before activating the min/max/average function. Test the circuit, otherwise the minimum reading will always be the ambient value before the test leads are connected. This will affect the analysis of the recorded data after the recording time has elapsed. When the Min/Search Max/Avg recording mode is activated, the multimeter will indicate the maximum reading on the display and will beep when a new maximum or minimum value is detected. Whining.
The advantage of this is that when ensuring that the digital multimeter will not be tampered with and will not pose a safety hazard to anyone, you can leave the digital multimeter in place for measurement and focus on other tasks. At any time during the recording cycle, you can view the saved readings, or pause recording mode without deleting the saved readings.
2. How a multimeter continuously records intermittent faults:
Some multimeters not only have min/max/average recording functions, but also combine this feature with another feature called AutoHOLD and larger memory to form Event Logging. Gong Qing. Automatic power maintenance can sense when the measurement signal becomes unstable and when it becomes stable again. Using the auto-hold function to trigger the start and stop of the minimum/maximum recording function allows the digital multimeter to not be limited to detecting faults that produce minimum or maximum values.
If the multimeter has an infrared RS232 interface, the continuous recording function will be more powerful, and it can become a simple event collector to transmit the data collected by the multimeter to the computer. Using computers, each stable and unstable event can be analyzed in detail. Not only can you view the minimum and maximum values within each stable and unstable period, but you can also view the start and end times of each period. In addition, the average value for each period is recorded. At the same time, the changing trend of voltage or current can be dynamically detected.
3. How does the multimeter mark the recording time:
The time when minimum and maximum values are detected is very useful information for determining the cause of intermittent failures. A digital multimeter in Min/Max/Avg recording mode can store the amount of time between starting a recording and saving a new minimum, maximum, or average value. Therefore, each saved minimum, maximum and average value has a corresponding "time stamp".
Nowadays, digital multimeters with digital acquisition or storage functions also have the same strip recording function through computers or their own memory. If the digital multimeter has a min/max/average recording mode function, like a tape recorder, the digital multimeter will read the input readings at regular intervals. But unlike a paper tape recorder that saves a reading, the reading is compared to the previously saved reading to determine if the value is higher than the previous maximum or lower than the previous minimum. If so, the new reading is replaced. The value originally held in the high or low reading register. After recording for a period of time, you can call up these registered values for display and view the maximum and minimum values within the recording time.
