How does a multimeter continuously record intermittent faults?
Some multimeters not only have the function of recording minimum/maximum/average values, but also combine this function with another function called AutoHOLD and larger memory, forming the power of Event Logging. Automatic maintenance can sense when the measurement signal becomes unstable and when it stabilizes again. By using the auto 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 it can become a simple event collector to transmit the data collected by the multimeter to a computer. By using computers, detailed analysis can be conducted on every stable and unstable event. You can not only view the minimum and maximum values during 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.
How to mark and record time with a multimeter
The time when the minimum and maximum values are detected is very useful information for determining the cause of intermittent faults. A digital multimeter can store the amount of time between starting recording and saving a new minimum, maximum, or average value in 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 the digital multimeter has a minimum/maximum/average value recording mode, like a paper tape recorder, the digital multimeter also reads the input readings at certain intervals. But unlike a paper tape recorder that stores individual readings, the reading is compared 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, the new reading will replace the value stored in the high or low reading register. After a period of recording, you can retrieve the values of these storage devices for display and view the maximum and minimum values during the recording period.
Just record the time when the minimum/maximum/average value recording mode is activated separately, and you can easily calculate the actual time when the digital multimeter detects the reading. For example, suppose you activated the recording mode at 3:07:00 pm and the displayed time stamp for the maximum reading is 47:05, simply adding the time stamp and the starting time can determine the time when the maximum value was recorded.
The use of the minimum/maximum/average value recording mode of a digital multimeter is very effective for diagnosing intermittent faults. However, it assumes that when a fault occurs, the circuit point connected to it will exhibit a maximum or minimum value j. If the readings caused by intermittent faults are between the maximum and minimum values, then the minimum/maximum/average function will not be very helpful in determining the cause of intermittent faults.
