# The polarity of the electrical plugs is important

## Measure with a measuring device

Measuring devices are sensitive and expensive. They are also expected to always work properly without having to run an extensive functional test every time. It is therefore important to follow a few basic rules when using a measuring device. After all, you should live a long time.

### Pay attention to the correct type of measurement

When measuring current, the measuring device has only a very small internal resistance. This means that the measurement result is not influenced as much as possible. Anyone who measures a voltage with an ammeter will damage or destroy the measuring mechanism.

### Pay attention to the polarity for direct voltage and direct current

If the polarity of a voltage or a current is not known, the measuring point should only be touched briefly with the measuring tip. In this way you can find out how the current or voltage is actually polarized. If the pointer moves from the zero point to the left, then the measuring lines have to be swapped. If the pointer moves to the right from the zero point, the polarity of the measuring device is correct.

### Resistance measurements only in the de-energized state

Resistances may only be measured when the device is de-energized and de-energized. Otherwise the measuring device will be damaged or destroyed! The circuit in which the resistor is built can also be damaged. In particular, because the measuring device supplies a current when measuring resistance. As a rule, it is sufficient to unsolder a soldered resistor on one side and then measure its value.
Charged capacitors also pose a risk to the measuring device. Capacitors, especially those with a very high capacity (aluminum electrolytic capacitors, gold caps, ...) can still have a voltage applied for a while, although the circuit has already been disconnected from the operating voltage.
Charged capacitors in the circuit must be discharged before the measurement. This is done by short-circuiting the individual capacitors, for example with pliers or a wire bridge.

### Use only measuring lines with perfect insulation and plugs

If the insulation of test leads is damaged, they must be replaced. Otherwise there is a risk of short circuits and unwanted electrical contacts. You should also take a look at the connectors. Corroded plugs lead to contact resistance and thus to incorrect measurement results.
Particularly when measuring the line voltage, one should pay attention to defective measuring lines and plugs. For your own well-being alone. If they are damaged, they should no longer be used, but should be replaced immediately!

### Take care when measuring the mains voltage (230 volts)

Seemingly banal, but a life-saving note: When measuring the mains voltage, the measuring plugs and measuring tips may only be touched on the insulated part. Otherwise there is danger to life and limb.
Furthermore, one should also note the following: In the case of power lines, inductive and capacitive interference often occurs. These are quite high resistance, i. H. these false voltages collapse with the slightest load. A multimeter usually has a very high internal resistance; H. these false voltages are hardly influenced and measured by him. A multimeter can still display voltages of 30 volts or more on a voltage-free line, even though it is actually voltage-free. A correct VDE measuring device or a Duspol can help here. These have lower internal resistances and cause these false voltages to collapse.

### Always select the largest measuring range at the beginning

To protect the measuring device from excessive voltages or currents, the largest measuring range must always be set at the beginning. If it is too large for reading the measured value, it can be reduced gradually.

### Always read the measured value in the upper third of the measuring range (analog measuring device)

In the case of analog measuring devices, the measuring range must be set so that the pointer is in the upper third of the measuring scale. The display of the measurement result is most accurate in this area.

### Adjusting the meter after use

A measuring device is a highly sensitive device that must be handled with care if it is to be reliable and to last for a long time. Therefore, each measuring device is set to the highest AC voltage range after use. You do this so that the next person who wants to measure and does not know how to use the measuring device can cause as little damage as possible.
The measuring device can withstand the most voltage in the highest voltage range. AC voltage because DC voltage does not matter to it. AC voltage in the DC voltage measuring range does, however. A current measurement on the voltage measuring circuit (high internal resistance = small current flow) does not cause any damage. The current measuring circuit (small internal resistance = large current flow), on the other hand, can be damaged when measuring a voltage.

### Product recommendations

#### Electronics simple and easy to understand

##### Electronics primer

The electronics primer is a book about the basics of electronics, components, circuit technology and digital technology.

I want that!

### Experience electronics with the "Starter Edition" electronics set

Perfect for beginners and newcomers

• Entry into electronics without prior knowledge
• Quick understanding of components and circuit symbols
• Experiment without a soldering iron: just insert components

More informationOrder the electronics set now