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Subject to change without notice

Introduction to the
operation of the HM 8040-3

First time operation

Before turning the instrument on please observe the following:

– The mains voltage selector at mainframe HM 8001-2 is set

to the correct voltage.

– The correct fuses for the voltage selected are installed in

the fuseholder

– Connection to a mains outlet with protective earth or to a

class 2 isolation transformer

– No visible damage to the instrument
– No damage to the line cord
– No loose parts inside the instrument

Turning the instrument on

After turning the instrument on the outputs will always remain
disconnected in order to protect the loads. First the desired
voltages should be set , then the desired maximum currents, then
the outputs may be activated by pressing OUTPUT

. After turn-

on the instrument will select the current limit mode (electronic
fuse deactivated). If the fuse mode is selected after turn-on this
mode will be lost after turn-off.

Survey of controls and displays

V/mA/Fuse

Short operation: switches displays back and forth between voltage
V and current mA
Long operation: switches back and forth between current limiting
and electronic fuse

V/mA/Fuse

(4 LEDs)

[V]

The voltage at the safety terminals is displayed with a
resolution of 0.1 V

[mA]

The output current is displayed with a resolution of 1 mA

[F]

If the electronic fuse was activated this LED will light up.

max

]

If current limit is reached, the lower LED lights up

Current limiting

After turn-on the instrument will be in the current limit mode. The
knobs CURRENT

allow to set the maximum output currents

for the left and right 20 V outputs independently of each other. If
the current limit in any one output is reached the current will
remain at the value I

max

set without affecting any other output. If

the current limit set of the remaining output should be reached
this output will also change over to constant current I

max

operation.

In order to set a current limit the output concerned has to be
shorted first, then the limit adjusted which is indicated by the
associated LED

lighting up. After removal of the short the

LED will extinguish.

Electronic fuse

Before selecting this mode the maximum currents of the 2
outputs have to be set according to the procedure outlined above.
The pushbutton V/mA/Fuse

is held depressed for a long

time, after the LED F

lights up the electronic fuse mode is

active. If any of the current limits set is reached all outputs will be
turned off completely. In order to leave the electronic fuse mode
press the pushbutton again long.

Example:

The left output may be in the current limit mode while the right
output may be in the electronic fuse mode. If I

max

is reached in the

left output current will continue to flow there. If the current limit
is reached in the right output, however, all outputs will be turned
off.

The current limits can be adjusted using the
rotary controls CURRENT

0 – 500 mA. In the

CCW position of these controls 0 A the current

will be indeed zero, so the output capacitances will be
discharged slowly to 0 Volt. In the Current Limit mode the
appropriate LEDs (I

max

) will light in the CCW position and

as explained the output voltage(s) will slowly decrease to
zero. In the Electronic Fuse mode all outputs will be
disabled immediately after pressing OUTPUT

if any of

the CURRENT controls is set CCW.

Displays

7segment 3 digit displays of either voltage or current. Each
display associates with the terminals underneath. The displays
show continuously the voltages resp. currents of the two 20 V
outputs, also while these are switched off. This allows presetting
the output levels prior to activating them which we do recommend.
Selection of voltage or current is done using the pushbuttons
V/mA/Fuse

. The voltages are displayed with a resolution of

0.1 V, the currents with 1 mA.

Output

Pushbutton for turning all outputs ON/OFF. The displays remain
unaffected always on. Activation of the outputs is indicated by the
LED [ON].

Overtemperature protection
If the internal temperature exceeds 75 .. 80 degrees

C the outputs and the displays will be switched off which is
indicated by 3 blinking dashes showing in the left and right
displays. As soon as the displays light up and show the values
set again the instrument is ready for operation. In order to
turn the outputs back on the pushbutton OUTPUT

has to

be depressed.

Introduction to the operation of the HM 8040-3

STOP

–

0 – 20 V

0.5 A

1 A

0.5 A

0 – 20 V

5 V

VOLTAGE