Is the effective value of the multimeter important?
Ordinary pointer multimeters or digital multimeters have frequency ranges for high-frequency voltage and current measurements. Beyond the frequency range they are true rms values that do not correctly reflect high frequency waveforms. Just look at the technical indicators of your multimeter and it will be clear.
What is True RMS?
Only true rms meters can measure voltage/current accurately. Its average value meter measures the AC signal. The calculation method is: the average value of the measured value × 1.11 = corrected to an effective value. The algorithm of the True RMS meter to measure the AC signal is: root mean square algorithm = true effective value. For pure sine waves, no matter it is a true RMS or average value meter, it can accurately measure, but for non-sine waves such as square waves, triangle waves, and sawtooth waves, only true RMS meters can accurately measure them. Nowadays, many electronic loads that have undergone frequency changes are non-sine waves, and only a true RMS multimeter can accurately measure the correct value.
How to avoid short circuit by measuring the voltage of each line on the circuit board with a multimeter
When measuring any circuit electronic components with a multimeter, you must first check the status of the multimeter before your test leads touch the electronic circuit components. For example, if you measure DC voltage, you must switch to the gear of DC voltage. How big, the first is to hit the gear to the highest gear. If you are measuring AC voltage, you must switch to the relevant gear for AC. If you don’t know the voltage, you can also switch to the highest gear first to measure. After turning to the highest gear and measuring the data, adjust the gear as needed for accurate measurement. Reminding everyone to check the status of the multimeter is to prevent some people from directly measuring the voltage when the multimeter is in the resistance or capacitance range, which may cause a short circuit to burn things. Therefore, before measuring anything, you must develop a number habit, that is, you must check the gear status of the multimeter, and then measure after confirming that it is correct.
1. A multimeter tip as sharp as possible
When I was studying and still in school, I followed a habit of my brother, that is, I like that the metal front ends of all the test leads of my multimeters are sharpened, and the sharp multimeter tips can contact the circuit board as small as possible. For the measurement of some small-area patch components, it can prevent the pen tip from being too thick to accidentally touch adjacent contacts.
2. Find extra black pens and transform them into crocodile clips
Find a pair of extra test leads, cut the black test lead, the end of the hand pen, and find a crocodile clip to solder it on for spare. Of course, if you don't want to do it yourself, you can buy ready-made ones, including red and black pens.
To measure the voltage of the circuit board, first determine whether the part of the circuit board to be measured is DC voltage or AC voltage. If it is DC voltage, first set the gear of the multimeter to the gear of DC voltage measurement, and then take a black pen in one hand and the other hand Take the red pen, and the black pen is the grounding terminal. Try to find the grounding point that is easy to put and touch as close as possible. Generally, the grounding point is a relatively large circuit board. The red pen is then separated to measure the circuit to be measured. At this time, the sharper the tip of the multimeter is, the more convenient it is to measure some fine chip component circuits. If the two hands are inconvenient to hold the test leads separately, as we said earlier, the spare test leads with crocodile clips can come in handy at this time, connect the black test leads with crocodile clips, and clip the crocodile clips to the circuit board. On the ground point, the red test lead can measure the entire DC circuit at will.
