How to find problems with multimeter
1, under the condition of charged, measure the key point or power-saving voltage, and judge whether the circuit is normal according to the voltage level;
2. Measure key points or power-saving current under live condition, and judge whether the circuit is normal according to the current;
3. In case of power failure, measure the resistance of the circuit and components, and judge whether the circuit is normal (short circuit, open circuit, etc.) if it is on or off.
Generally, multimeter only uses two gears to check electrical faults, one is voltage gear (including AC/DC voltage gear) and the other is ohm.
If the equipment doesn't work, the first thing you think about is whether the voltage of the equipment is normal, so you need to use the voltage range of the multimeter (choose AC voltage range or DC voltage range, depending on whether your equipment is AC equipment or DC equipment) to measure. If the control loop or the secondary loop is disconnected, you should also use the voltage file to measure whether the voltage at a certain place is normal if you are familiar with the schematic diagram. If it is determined that the voltage at that place is not there, it means that there is disconnection or poor contact. In order to further determine whether there is a problem at this place, you have to disconnect the power supply of the equipment at this time, and there is an ohmmeter to determine whether there is indeed a disconnection at this place, so as to eliminate the fault. Roughly, it mainly depends on your familiarity with the equipment and the accumulation of experience in your work. If you have any questions, please ask.
1. How to record intermittent faults with multimeter:
Use the minimum/maximum/average value recording mode of multimeter, and select the corresponding functions (AC voltage, DC voltage, resistance, AC current, DC current and frequency) according to the measured items, so as to ensure that the test circuit is connected before activating the minimum/maximum/average value function, otherwise the minimum 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. J Activate the minimum/search maximum/average recording mode, the maximum reading will be indicated on the display screen of the multimeter, and a buzzer will be sounded when a new maximum or minimum value is detected.
The advantage of this is that the digital multimeter can be kept in place to measure and concentrate on other work while ensuring that it will not be tampered with and will not pose a potential safety hazard to any man-made. At any time during the recording cycle, you can view the saved readings, or pause the recording mode without deleting the saved readings.
2. How to continuously record intermittent faults with multimeter:
Some multimeters not only have the minimum/maximum/average value recording function, but also combine this function with another function called AutoHOLD and a larger memory, thus achieving the function of EventLogging. Auto-hold power coefficient 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 value recording function will make the digital multimeter not only detect those faults that produce the minimum or maximum value.
If the multimeter has an infrared RS232 interface, it will be more powerful to continuously record the power factor, and it can become a simple event collector to transmit the data collected by the multimeter to the computer. With the help of computers, every stable and unstable event can be analyzed in detail. You can view not only the minimum and maximum values in each stable and unstable period, but also the start and end time of each period. In addition, the average value of each cycle is recorded. At the same time, the trend diagram of voltage or current can be dynamically detected.
3. How to mark the recording time with multimeter:
The time when the minimum and maximum values are detected is very useful information for determining the cause of intermittent failure. In the min/max/average recording mode, the digital multimeter can store the amount of time from the beginning of recording to saving a new minimum, maximum or average. Therefore, each saved minimum, maximum and average has a corresponding "time stamp".
Now, the digital multimeter with digital acquisition or storage function has the same ribbon recording function through the computer or its own memory. If the digital multimeter has the power arrow of the minimum/maximum/average recording mode, like the paper tape recorder, the digital multimeter also reads the input readings at certain intervals. However, unlike the paper tape recorder, which saves a reading, it compares the reading with the previously saved reading to determine whether the value is higher than the previous maximum value or lower than the previous minimum value J. If so, it will replace the value originally saved in the high or low reading register with a new reading. After a period of recording, you can call up the values of these registers and display them to see the maximum and minimum values during the recording time.
