HP 6038A - 3-46 MODE SWITCHES; 3-49 HP-IB

3-44 If slightly degraded CV load regulation can be tolerated,
the power supply will provide remote voltage sensing with up
to 2 Vdc drop in each load lead and with more than 0.2 ohms
resistance in each sense lead. As the voltage drop in the load
leads Increases, the load voltage error due to sense-lead
resistance increases according to the formula:
{2Rs +0.5} Vi
1000
where Rs is the resistance in ohms of each sense lead and VI
is the voltage drop in each load lead. For example, if the
resistance in each sense lead is 1 ohm and the voitage drop
in each load lead is 2 Vdc, the load voltage is about [2(1)
+ 0.5)2/1000 = 1.25 mVdc less than with zero sense-lead
resistance.
3-45 The sensing leads are part of the supply's program¬
ming circuits, so they should be connected in such a way as
to make it unlikely that they might inadvertently become open
circuited. If the sense leads open during operation, the voltage
at the load may rise above its programmed value.
The power supply includes protection resistors
which reduce the effect of open sense leads dur¬
ing remote-sensing operation. If the +S lead
opens, the output voltage increases about 4%
and is sensed between the + OUT terminal and
the negative side of the load. If the -S lead
opens the output voltage increases about 1 % and
is sensed between the positive side of the load
and -OUT. If both sense leads open, the out¬
put voltage increases about 4.8% and is sensed
locally.
3-47 Table 3-4 shows six switches on the rear panel that
configure the power supply for digital programming (either HP-
!B or front-pane! RPG) or analog programming (resistance or
voitage). (Note that front panel programming is digital; the RPG
produces pulses that are monitored by the microprocessor,
which then raises or lowers the digital input to the DACs that
control the power supply output.) Table 3-4 shows the proper
switch settings for each programming mode. When shipped
from the factory the switches are set for HP-IB/front-panel-
Table 3-4. Mode Swftches
Mode
Svntches
Programmli^ Mode
hp-is;rfg Voltage Reastance
B6 0
0
1
CV
B5 0 0 0
Circuits B4 1 0 0
B3 0 0 1
CC B2
0 0 0
Circuits B1 1 0 0
RPG programming, which is the normal operating mode for this
power supply. The two analog programming modes are
available for use in special circumstances.
3-^ Typically, only one programming mode is used for both
output parameters (voltage and current). However, the mode
switches allow voltage and current to be programmed in¬
dependently. For example, voltage could be programmed
digitally, either via HP-IB or front panel, while current is
resistance programmed. Note that only one programming mode
can be used for each parameter at one time. (For example, it
is not permissible to superimpose an analog programming
voltage on the digital programming signal. To do so could cause
programming errors.)
3-K) Connections between the power supply and the HP-
IB are made via the HP-IB connector on the rear panel. Figure
3-7 shows the signals at each of the HP-IB connector pins. The
HP-IB connectors table in Section 1 lists cables and cable ac¬
cessories that are available from HP. The HP-IB connector uses
metric threads, which are colored black. Cables manufactured
prior to 1975 have non-metric fasteners, which are colored silver.
Do not attempt to mate non-metric (silver) fasteners with
metric (black) fasteners (see accessories table for conversion
kit).
SIGNAL COMMON
fS5
PO
SHIELD
SIGNAL COMMON
TWISTED WITH PIN II
ro
=
ATN
SIGNAL COMMON
TWISTED WITH PIN 10
t\>
fV3
5
SRQ
SIGNAL COMMON
TWISTED WITH PIN 9
ro
(0
IFC
SIGNAL COMMON
TWISTED WITH PIN 8
fV7
o
CD
NDAC
SIGNAL COMMON
TWISTED WITH PIN 7
NRFO
SIGNAL COMMON
TWISTED WITH PIN 6
CO
cti
OAV
PEN
tjl
EOl
DIOS
»
DI04
DI07 5
0103
DIOS
X
ro
0102
0105
-
DIOI
Figure 3-7. HP-IB Connector
3-51 An HP-IB system may be connected together in any
configuration (star, linear or combination) as long as the
3-9