User manual

Multimeters differ mainly regarding what they can measure. Of course, this does
not mean that a simple instrument is self-explanatory. Look at the large
adjustment wheel that sets the different measuring areas and values precisely.
What is offered? What do you need at all? These questions should be answered
before making your purchase.
Also deal with the strings. They have different colours (red: plus pole; black:
minus pole). Learn about your device using the operating instructions before
using it for your first measurements.
Figure 16: First get to know the instrument. A detailed look into the operating
instructions helps with this.
CAT certification devices on the area of application. Multimeters must meet
various protection criteria that warrant their safe use. Finally, measurement of
current and voltages is not a game, but associated with risks!
Multimeters must be designed for a combination of constant voltages and so-
called transient overvoltages. These protective measures are classified in 4 CAT
classes. The higher the CAT class, the more diversely can the instrument be used.
CAT Classes
CAT I
Multimeters with CAT-I certification have only little protective measures. They
must only be used for measurements in protected electronics areas and to perform
measurements at devices. They must have a sufficient protection against
transient overvoltages.
CAT II
CAT-II-capable instruments permit use for single-phase loads connected to a
mains socket. This includes household appliances and portable tools. Mains
sockets and lines must only be measured with limitations. Multimeter for
electronics enthusiasts should have at least CAT II.
CAT III
Multimeters with CAT-III approval are already suitable for use in three-phase
distributor grids and single-phase commercial lighting. They can already measure
rotary current motors or power sockets for high loads.
CAT IV
CAT IV additionally permits use from the rotary current connection of the power
plant and at overhead lines. These therefore are devices for measurements that a
private person must not perform.
Correctly Connecting the Measuring Strings
Only few multimeters have the measuring lines connected right to the multimeter.
Usually, the devices have 3 to 4 sockets to which the measuring strings can be
connected. This generally must only take place when they have not been connected
yet!
The black string corresponds to the minus line in the wider sense (return line).
It is connected to COM. In which socket the right measuring line needs to be
connected