34
Operation modes
6 Operation modes
6.1 Constant voltage operation (CV)
The HM8143 programmable power supply features va-
rious different operating modes. Of these, it is probably
used most often as a voltage source. This is the nor-
mal mode and is indicated by the CV (constant voltage)
LEDs or beside the displays (in this mode V
actual
= V
set
and I
actual
< I
limit
. Here, the displayed values represent
the measured output voltages and the measured output
current.
6.2 Constant current operation (CC)
As soon as the output current reaches the programmed
current limit value, the power supply automatically swit-
ches into its current source mode, if the electronic fuse is
not activated (see chapter Electronic Fuse). This mode is
indicated by the CC (constant current) LEDs or (now I
actual
= I
limit
and V
actual
> V
set
); the CV LEDs or extinguish. The
measured output voltage generally drops below the pro-
grammed voltage. The actual measured value can be read
off the display. This mode is only possible if the electro-
nic fuse is not active (FUSE LED is off) see chapter electro-
nic fuse.
6.3 Electronic load
The HM8143 also offers a mode in which it functions as an
electronic load (current sink). The instrument goes into this
mode automatically, and it can be recognized by a nega-
tive sign (–) in front of a displayed current value. The same
limit values apply to voltage and current as in normal ope-
rating mode. In this operation mode the output voltage
measured is normally greater than the nominal value (V
ac-
tual
>
V
set
)
6.4 Series and parallel mode
To increase the output voltages and currents, the two
channels of the power supply can be connected either in
series or in parallel.
It is important to keep in mind that when the two output
circuits are connected in series a greater voltage than that
ordinarily permitted for safety reasons can develop. The
HM8143 may therefore be used only by personnel who are
familiar with the associated risks.
6.5 Arbitrary waveform mode
By interface the HM8143 can also be made to generate
freely programmable waveforms within the limit values set
(arbitrary mode). See chapter Arbitrary.
If you are using the modulation then it is not allowed to use par-
allel setup, otherwise the instrument may be destroyed.
7 Safety features
The HM8143 is equipped with a variety of safety features
to prevent damage being caused to the instrument by
short circuits or overheating.
7.1 Current limit
If one of the output voltages is short circuited, the current
limiter automatically keeps the current from rising beyond
the programmed maximum output current. The response
time is approx. 200 µs that means during this time the ma-
ximum current value set can be exceeded.
7.2 Electronic fuse
In order to provide a still better protection than current li-
miting offers the HM8143 features an electronic fuse. As
soon as I
max
is reached all outputs will be immediately si-
multaneously disabled.
They may be turned on again by depressing OUPUT. The
electronic fuse is activated by operating the FUSE button.
The FUSE LED is on. By pushing the FUSE button again, the
electronic fuse is deactivated. The fuse LED is dark.
7.3 Cooling
The heat generated in the HM8143 is removed by a tem-
perature controlled fan. This is located together with the
heat sink in a “cooling channel“ that runs straight through
the instrument. Air is drawn in on the righthand side of the
unit and blown out again on the lefthand side. This also
prevents excessive dust accumulation. Always make sure
that there is sufficient open space for cooling on both si
-
des of the HM8143.
If the temperature inside the HM8143 should nevertheless
rise to above 80 °C, an automatic temperature-controlled sa-
fety circuit is activated. The outputs are put off. After the unit
has cooled down sufficiently, operation can be resumed by
pressing the OUTPUT button.
7.4 Error messages
In case of a mal function the HM8143 will display an error
message on the left display (channel 1):
Display Meaning
E1
Error channel 1
E3
Error channel 2
E2
Error channel 3
Please turn off the instrument if one of these errors oc-
curs. If the error is still displayed after resetting the instru-
ment, it has to be sent in. Please contact the HAMEG ser-
vice department (Tel: +049 (0) 6182 800 500, E-Mail: ser-
vice@hameg.com).
In no case may the cooling holes on the sides of the unit be
covered.
