How to repair the deformation of the needle of the pointer multimeter to measure the battery voltage
It is necessary to open the front panel of the case and carefully straighten the hands. This is a delicate job that requires carefulness, but it is not difficult. For pointer multimeters, the red test lead must be connected to the positive pole, and the black test lead must be connected to the negative pole. When measuring a higher voltage, the test leads are reversed, and it is easy to bend the test needle. Nowadays, digital multimeters are also cheap, and the reverse connection of the test leads is just a minus sign before the number. It is recommended that for those who are not familiar with the use of multimeters, directly buy a digital multimeter that does not need to change the range, and the red and black test leads can be connected casually, and the meter will not be burned.
You only need to disassemble the back cover, then remove the screw behind the panel, and then screw the needle finger straight. There is a limit rod on both sides of it. The pointer is close to the right limit rod and then moves a little to the right. That's it, be sure to let the pointer point to the 0 position.
The pointer multimeter uses current, and the voltage range does not have reverse connection protection. Important things must be said three times, otherwise the coil under the pointer will be easily overloaded and burned, and you will have to buy a new one if you don’t have accessories.
Personally, I feel that there is no problem with measuring the voltage of the tube with the pointer meter. If you want to measure accurately, it is recommended to use a digital multimeter. This kind of multimeter has a reverse connection circuit. If your test lead is connected to the wrong measurement point, it will only display negative measurements. value, and then just ignore the minus sign.
When using it, the voltage gear should be selected correctly, and generally the hands of the watch will not be bent. Those who have hands-on ability can restore the pointer of the watch, and pay attention to the balance of the pointer when repairing. (Note: If there is any change in placing the meter body flat, upright, or sideways, this is the key to repairing the meter), otherwise the meter will not be correct.
Using the capacitance file of the digital multimeter can not only measure the actual capacity of the capacitor, but also judge the quality of the measured capacitor through the displayed reading. The following is an introduction to the method of using the capacitance file of a digital multimeter to judge whether a capacitor is good or bad.
A digital multimeter measures an aluminum electrolytic capacitor with a nominal value of 47μF/35V.
Here we take the commonly used aluminum electrolytic capacitor as an example to introduce the specific measurement method. First, adjust the range switch of the multimeter to the proper position of the capacitance gear according to the size of the measured capacitance, and then touch the two pins of the electrolytic capacitor with red and black test leads (don’t need to consider the polarity of the test leads). The nominal value of the capacitor is basically the same (the actual capacity of the capacitor has a certain deviation from its nominal value), which means that the capacitor is good.
What is measured is an aluminum electrolytic capacitor with a nominal value of 47μF, and the displayed capacity is 48.95μF, and the error is within the allowable range, indicating that the capacitor is good.
When using a digital multimeter to measure capacitance, if the measured capacity is significantly greater than its nominal value, it means that the capacitance has a large leakage current and should not be used. If when measuring a certain capacitance, the reading displayed on the capacitance file is "1", and the resistance value of the capacitor measured by the resistance file of the multimeter is very small, it means that the capacitor has been broken down and damaged.
