How to use a multimeter to help you find the problem
1. Under live conditions, measure key points or energy-saving voltage, and determine whether the circuit is normal based on whether the voltage is high or low;
2. Under live conditions, measure key points or energy-saving currents, and determine whether the circuit is normal based on the magnitude of the current;
3. In the event of a power outage, measure the resistance of the circuit and components to determine if the circuit is functioning properly (short circuit, open circuit, etc.).
A multimeter usually only uses two levels to check for electrical faults, one is voltage level (including AC and DC voltage levels) and the other is ohms.
If the device is not working, the first thing that comes to mind is whether the voltage of the device is normal. You need to use the voltage range of a multimeter (choose AC voltage range or DC voltage range, depending on whether your device is AC or DC) to measure. If the control circuit or secondary circuit is disconnected, even if you are familiar with the schematic, you need to use a voltage range to measure whether the voltage at a certain location is normal. If it is determined that the voltage at that location should not be present but rather present, and what should be present but not present, it indicates that there is a disconnection or poor contact at that location. In order to determine more accurately whether there is a problem in that area, you also need to disconnect the power supply of the device. The ohm range of a multimeter should be used to determine if the wire is indeed disconnected in that area, in order to troubleshoot. Roughly speaking, it mainly depends on your familiarity with the equipment and accumulation of work experience. If you have any further questions, please feel free to ask.
How to record intermittent faults with a multimeter:
Using the minimum/maximum/average value recording mode of a multimeter, select the corresponding function (AC voltage, DC voltage, resistance, AC current, DC current, and frequency) according to the measurement item, and ensure that the test circuit is connected before activating the minimum/maximum/average value function. Otherwise, the minimum value reading will always be the environmental value before the test line is connected. This will affect the analysis of the recorded data after the end of the recording time. The minimum/search maximum/average recording mode will be activated, and the maximum reading will be indicated on the multimeter display screen. When a new maximum or minimum value is detected, a buzzing sound will be emitted.
The advantage of this is that while ensuring that the digital multimeter is not tampered with and does not pose any safety hazards to humans, the digital multimeter can be left in place for measurement and focused on other tasks. At any time during the recording cycle, you can view saved readings or pause the recording mode without deleting the saved readings.
How to continuously record intermittent faults with a multimeter:
Some multimeters not only have the function of recording minimum/maximum/average values, but also combine this function with another function called AutoHOLD and a larger memory to enhance Event Logging function. The automatic maintenance function can sense when the measurement signal becomes unstable and when it stabilizes again. By using the automatic hold function to trigger the start and stop of the minimum/maximum value recording function, the digital multimeter is not limited to detecting faults that generate minimum or maximum values.
If the multimeter has an infrared RS232 interface, the continuous recording function will be more powerful and can become a simple event collector, transmitting the data collected by the multimeter to the computer. By using computers, detailed analysis can be conducted on each stable and unstable event. You can not only view the minimum and maximum values within each stable and unstable cycle, but also the start and end times of each cycle. Additionally, record the average value for each cycle. At the same time, it can dynamically detect the trend of voltage or current changes.
3. How to mark the recording time with a multimeter:
The time taken to detect the minimum and maximum values is very useful information for determining the cause of intermittent faults. The digital multimeter can store the amount of time from the start of recording to saving new minimum, maximum, or average values in the minimum/maximum/average recording mode. Therefore, each saved minimum, maximum, and average value has a corresponding "time stamp".
Nowadays, digital multimeters with digital acquisition or storage capabilities also have the same strip recording function through computers or their own memory. If a digital multimeter has a minimum/maximum/average recording mode arrow, like a tape recorder, the digital multimeter also reads the input readings at certain intervals. But unlike paper tape recorders that store individual readings, comparing the readings with previously saved readings to determine if the value is higher than the previous maximum value or lower than the previous minimum value. If so, the new reading will replace the value originally stored in the high or low reading register. After a period of recording, you can retrieve the values of these registers for display, and view the maximum and minimum values during the recording time.
