In which situations should a multimeter not be used?
A multimeter is one of the most important tools for electricians, because it is simple and practical. It can be said that every electrician has at least one hand, with a huge amount of inventory. It can measure on-off, voltage, current, and even some electronic components. It seems to be omnipotent and has particularly strong comprehensive ability, which is also the origin of the name multimeter.
We often say that a multimeter can be used this way or that way. Every time we repair it, the multimeter is always in our hands. But have we ever thought about the situation where a multimeter cannot be used or cannot be used?
Today, let's talk about the shortcomings of a multimeter. First of all, it can measure current. A multimeter can actually measure current, but it must be connected in series in the circuit when measuring current, otherwise it cannot be used. In general, it is very unsafe to connect a multimeter in series in the circuit to measure high current. On the other hand, sometimes the circuit needs to be disconnected and connected in series. Therefore, multimeters are not very commonly used or practical for measuring current!
Secondly, it is necessary to measure the insulation resistance of ground resistance and motor cables, as the power source used for multimeters is batteries with low voltage. However, measuring the insulation resistance of ground resistance, cable motors, etc. is relatively high. In general, it is difficult for multimeters to measure their effective resistance, and even if they are measured, the error is usually large, even incorrect values, which have no practical reference value and can sometimes be misleading. Therefore, it is not recommended to use a multimeter in this situation.
There is another situation where the multimeter cannot be used, which is the battery capacity. People often say that my electric scooter has just
been charged and runs out of battery after driving for a while. Is it because the battery is broken? This so-called battery failure is actually due to a decrease in battery capacity, and the multimeter cannot be used for such problems!
