Current Limiting; Electronic Fuse; Concept Of The Hm8040 - Rohde & Schwarz Hameg Instruments HM8040-3 Manual

B a s i c s o f p o w e r s u p p i e s
Fig. 3: Parallel operation
Example:
A load draws 0.7 A at 12 V. Each output of the
HM 8040-3 is specifi ed for 0.5 A. In order to supply
the 0.7 A both outputs have to be set to 12 V. Then
the respective output safety terminals have to be
connected in parallel (black to black, red to red).
The load is connected to one of the supplies. By
depressing OUPUT
As a rule one output will supply appr. 500 mA
in current limit mode, the other the balance of
200 mA in voltage control mode.
If you parallel power supplies made by
HAMEG and those of other manufacturers
please make sure that the individual cur-
STOP STOP
rent contributions of the supplies involved
are as equal as possible. HAMEG supplies
are designed for series and parallel
opera-tion. If supplies of other manufac-
turers are used in a parallel connection
which are not overload protected damage
may occur if the individual currents are
unequal.

Current limiting

means that a maximum current can be set. This
U
out
U
const
Adjustment of current
Current limit
22
Subject to change without notice
the outputs are activated.
I
I
max
is e.g. useful in order to protect a sensitive test
circuit. In case of an inadvertent short in the test
circuit the current will be limited to the value set
which will in most cases prevent damage.
The picture shows that the output voltage V
remains stable, while the current I increases until
the current limit selected will be reached. At this
moment the instrument will change from constant
voltage regulation to constant current regulation.
Any further load increase will cause the current
to remain stable while the voltage decreases
ultimately to zero.

Electronic fuse

This feature provides a still better protection of
sensitive loads, especially of such loads which re-
quire more than one voltage: if one current limit is
reached all output voltages will be dis-connected
immediately. In order to turn these back on the
pushbutton OUTPUT

Concept of the HM8040-3

The triple power supply HM8040-3 features 3 in-
dependent output voltages. In addition to supplying
3 voltages the 0 ... 20 V outputs may be connected
in series or parallel.
Exceeding 42 V
If all outputs are series connected the
sum can exceed 42 V. In this case tou-
ching of live parts may cause danger
of life! It is assumed that only qualifi ed
and extensively instructed personnel is
allowed to operate these supplies and
their loads.
In series connection the maximum current is
0.5 A. By paralleling the outputs a maximum of
1 A is possible. The maximum voltage remains
20 V. Please note that the specifi cations (e.g. im-
pedance, noise, regulation) listed for individual
use of the outputs may change if series or parallel
out
connected.
out
must be depressed.