Gossen MetraWatt SSP 120 Series, Operating Instructions Manual

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GMC-I Messtechnik GmbH 57
5.11 Varying the Internal Output Resistance Value
Functions

In the voltage regulating mode, internal output resistance has a
value of close to 0

.

The internal output resistance value can be increased for
certain applications, for example
simulation of long output cables
or weak automotive batteries .
The selected (open-circuit) output voltage is reduced in
proportion to increasing load (Figure 5.11 a).
Figure 5.11 a Dependence of Output Voltage
on Load
Standardization

The standard characteristic curve shown in Figure 5.11 c is
valid for all KONSTANTER models.

Quick and easy determination indicating which output
resistance R
i
correlates to any given control resistance R
ext
is
made possible with the curve.
R
i
= R
imax

display value
Connection

Connect the analog interface as shown in Figure 5.11 b.

The following relationship between internal resistance R
i
and
control resistance R
ext
applies with this wiring configuration:
Example: U
nom
= 40 V, I
nom
= 6 A, R
i
is 0.5

===> R
ext
= 376 k

Figure 5.11 b Wiring for Varying Internal Resistance

Table of R
imax
Values for All KONSTANTER Models
Figure 5.11 c Standardized Curve for Determining Internal Output Resistance for a Specified Control Resistance
U
nom
I
nom
U/V
I / A
ISET
USET
0
R
L
R
L

Ri
m
ax

R
ext
=
0
Ri
min

R
ext

R
ext

Device Type 120-20 120-40 120-80
R
imax
/

2.46 8.2 32.8
Device Type 240-20 240-40 240-80
R
imax
/

1.23 4.1 16.4
R
ext
=
30 k


U
nom
R
i

I
nom

24.4 k

SSP KONSTANTER
+ SENSE

OUT

OUT

SENSE
Analog Interface
SIG1 OUT
SIG2 OUT
TRG IN

TRG IN

+15 V
AGND
Uset

Uset +
Iset +
U-MON
I-MON
+ OUT
+ OUT
R
ext
Output
Settings
USET = Uset
ISET = Iset
Output on / off
R
load
R
imax
R
i
R
ext
/W
10
10
2
10
3
10
4
10
5
10
6
10
7
10
8
10
-4
10
-3
10
-2
10
-1
1
R
imax
= 1.23

U
nom
I
nom
R
imax
24.4 k

R
ext
+24.4 k

R
i
=
;