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Introduction to using the HM8142
When the HM8142 is powered up it automatically performs a
self test routine, which checks all of the unit's important func-
tions and the contents of the internal memories and registers.
While self-testing is going on, all of the frontpanel LEDs light
up together and the version number of the EPROM appears in
the top righthand display (for the 2
sting has been completed, the HM8142 is restored to the same
operational state that it had been in before last being switched
off. All that is left to do before actually using it is to press the
OUTPUT button
to enable the outputs. This approach was
selected in order to prevent damage being inadvertently caused
to connected loads because the stored voltage or current set-
ting might be too high for the application at hand.
Setting output voltages and the current limiter
The changeable parameters (output voltages and current
limit) are set using 3 controls situated in the middle of the
instrument's front panel (rotary knob
). To change values, fi rst select the appropriate parameter
with the V
and I
buttons. Then use the rotary knob
SET
SET
to quickly set the desired value.
If the UP/DOWN button
is held depressed, after a short time
an autorepeat feature is activated, incrementing or decremen-
ting the value in 10 mV or 1 mA steps.
The HM8142 normally displays the actual values; in otherwords,
the output voltage and current values measured by the instru-
ment are displayed. The controls (rotary knob
buttons
) are disabled in this mode. The programming mode
is activated by briefl y pressing one of the V
tons. The LED next to the button lights up to indicate that this
mode is active, and the corresponding target value appears in
the display. The controls are now enabled for programming.
The desired output voltage or a value for current limitation can
be input. If more than about 10 seconds elapse without any of
the controls being pressed or manipulated, than an automa-
tic time out function switches the HM8142 back to its normal
operating mode.
Resolution
The attainable resolution with the rotary knob
voltage and 10 mA for current. If a greater resolution is neces-
sary, it can be achieved by using the UP/DOWN buttons
mV steps and 1 mA current increments are programmable in
this way. The resolution of the display does not change.
All manuals and user guides at all-guides.com
nd
output voltage). Once te-
and UP/DOWN buttons
and UP/DOWN
or I
but-
SET
SET
is 100 mV for
. 10
O p e r a t i n g m o d e s
Operating modes
Constant voltage operation (CV)
The HM8142 programmable power supply features various
different operating modes. Of these, it is probably used most
often as a voltage source. This is the normal mode and is in-
dicated by the CV (constant voltage) LEDs in the displays (in
this mode V
= V
and I
actual
set
actual
values represent the measured output voltages and the
measured output current.
Constant current operation (CC)
As soon as the output current reaches the programmed cur-
rent limit value, the power supply automatically switches in-
to its current source mode. This mode is indicated by the CC
(constant current) LEDs (now I
CV LEDs extinguish. The measured output voltage generally
drops below the programmed voltage. The actual measured
value can be read off the display.
Serial or parallel operation
To increase the output voltages and currents, the two chan-
nels 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 HM8142 may
therefore be used only by personnel who are familiar with the
associated risks.
Electronic load
The HM8142 also offers a mode in which it functions as an elec-
tronic load (current sink). The instrument goes into this mode
automatically, and it can be recognized by a negative sign in
front of a displayed current value. The same limit values apply
to voltage and current as in normal operating mode.
Arbitrary waveform mode
By interface the HM8142 can also be made to generate freely
programmable waveforms within the limit values set (arbi-
trary mode).
Trigger Input + Trigger Output (Start/Stop)
In order to permit easy triggering of an oscilloscope connected
to the output of the HM8142, especially in arbitrary mode, the in-
strument is equipped with a BNC socket TRIGGER IN/OUT
its rear panel. This is confi gured as a tristate output and permits
a trigger signal to be taken after each signal period in arbitrary
mode, or the arbitrary function to be activated by an external
trigger signal.
Modulation inputs
By virtue of the modulation inputs on its rear panel, the HM8142
can also be used as a modulated power amplifi er. These in-
puts have a gain by a factor of 10. The frequency range (3 dB)
extends from DC to 8 kHz.
< I
. Here, the displayed
limit
= I
and V
= V
); the
actual
limit
actual
set
on
21
Subject to change without notice
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