Hameg HM8040-3, Руководство пользователя, Страница: 18 / 22

18 Subject to change without notice
Basics of power supplies
Linear regulators
Linear regulators offer a very constant output voltage even if the
mains or the load may vary considerably. The remaining ripple will
be very low with any good instrument, about 1 mV
rms
or less and
may be neglected. Also, linear regulators are free from EMI as
generated by SMPS.
A conventional mains transformer isolates the instrument from
the mains. A recitifier provides an unregulated dc voltage buffe-
red by capacitors which also serve as energy storage elements.
A transistor in series with the output is controlled by a regulation
loop which compares (a fraction of) the output voltage with a
highly stable reference voltage. This analog loop is very fast and
will restore the output voltage quickly to its desired value whenever
the input voltage or the load vary.
Parallel and series operation
Supplies must be specified for these operating modes which is
the case with all HAMEG supplies. The output voltages to be
combined are normally independent of each other. The outputs of
one or more supplies can then be connected in series or parallel.
Series operation
Danger! High voltage!
As you see the voltages are added. The total voltage generated
thus may exceed the 42 V safety limit. In such case touching live
parts may create danger of life! It is assumed that only qualified
and extensively instructed personnel is allowed to operate such
power supplies and their loads. All outputs carry the same
current, hence the current limit adjustments of all supplies should
be set to the same value. If in any of the series connected power
supplies the current limit will be reached this supply will enter the
current limiting mode, so the total output voltage will decrease
and become unregulated!
OUTPUT Turns outputs on/off
5 V 1 A 5 V output, adjustable within ±10% of 5 V
with a screwdriver.
Max. 1 A, short-circuit proof.
20 V output on the left
V/mA/Fuse Selection of voltage or current display V/mA
Selection of current limiting or electronic
fuse function
Display 3 digit display (7segment LED)
V LED voltage display selected
mA LED current display selected
F LED of electronic fuse activated
I
max
LED indication of current limit reached
VOLTAGE Adjustment of voltage 0 .. 20 V
0 – 20 V Safety terminals for left 20 V output
CURRENT Adjustment of current limit Imax = 0 .. 0.5 A
20 V output on the right
V/mA/FUSE Selection of voltage or current display.
Selection of current limiting or electronic
fuse function.
Display 3 digit display (7segment LED)
V LED voltage display selected
mA LED current display selected
F LED of electronic fuse activated
I
max
LED indication of current limit reached
VOLTAGE Adjustment of voltage 0 .. 20 V
0 – 20 V Safety terminals of right 20 V output
CURRENT Adjustment of current limit I
max
= 0 .. 0.5 A
Designition of operating controls
Power supply 1
Output 1
+
-
Power supply 1
2 Output
+
-
Power supply 2
1 Output
+
-
U
3
U
2
U
1
U = U + U + U
total
1 2 3
I = I = I = I
total
1 2 3
I
2
I
3
I
1
Designition of operating controls
– – – + + +
0 – 20 V
0.5 A
1 A
0.5 A
0 – 20 V
5 V
VOLTAGE CURRENT VOLTAGE CURRENT
V
OUTPUT
TRIPLE POWER SUPPLY HM8040-
3
Instruments
F F
ON
PUSH LONG
FUSE
ON/OFF
mA
V
FUSE
ON/OFF
mA
8
1 2 3 4 5 6 7
9 10 11 12 13 14
AC
voltage
Line transformer rectifier actuator
analog controller
output
reference voltage
REF
DC
voltage
GND
C1
OPVA
C2
B1
TR1