VI-700 V&l Source
6
OPERATION
not assert control, the front panel thumbwheel output
value is supplied. The
REMOTE
and
LOCAL LEDs
always indicate which interface is controlling theoutput
value.
Setting the front panel
REMOTE/LOCAL
switch
to
LOCAL
overrides
the REMOTE option settings
and
always
sets the output to the value selected us-
ing the front panel thumbwheels, regardless of the
REMOTE option’s assertion of control.
For IEEE and RS232 units, the
LOCAL
indicator
remains on until communication with the unit is initial-
ized. The mode changes to
REMOTE
after con-
troller commands are received.
Set the
MULTIPLIER
on the front panel manually.
The
MULTIPLIER
is not under
REMOTE
con-
trol.
Set the output level remotely, replacing the front panel
thumbwheel setting. See Chapter on IEEE-488 pro-
gramming.
3.3.2.2 BCD Control
Units with a
BCD
option provide a connector on the
rear panel for inputting a 3-1/2 digit BCD equivalent
of the thumbwheel setting. This digital input is opera-
tive whenever the
CNTRL
MODE
switch is set to
REMOTE.
The
MULTIPLIER
switches must be
manually set.
The digital output pin assignments are given below in
Table 3. 1. The digital output connector is a 26 pin
header on the rear panel. It may be mated to many
popular female connectors such as
3M Company
Model 3399,
GTE Sylvania Inc.
Model 6BAXX-26-
lXX-Y.X,
T&B/Ansley Corp.
Model 609-2600M or
equivalent. The rear panel connector pin numbering,
as the connector is viewed straight on, is also shown
in Table 3. 1.
The required input is a 5
V, positive true TTL com-
patible source.
3.4
Setting of Output Level
IMPORTANT:
The VI-700 must be allowed
to warm up for 15 minutes to reach specified accu-
racy. For maximum stability and minimum drift, al-
low the unit to
warm up for at least one hour.
The front panel controls simultaneously set both the
voltage and current output levels. This output may
be conveniently and directly read on the front panel.
The output in volts and milliamperes is exactly the
MULTIPLIER
setting times the number shown on
the thumbwheel switches. For example, a setting of
X10 and 1.335 outputs 13.35 V and 13.35 mA; a set-
ting of X0.1 and .025 outputs 2.5 mV and 2.5
µ
A.
The range used, i.e. X10, Xl, or X0.l, should be the
one providing the highest resolution. If 10 mV is re-
quired, for example, it should be obtained on the X0.1
range even though it is available on the Xl range. This
allows for maximum accuracy even though all set-
tings on an ranges will meet performance specifica-
tions.
In the case of a
REMOTE
input being used, it over-
rides the thumbwheel setting.
3.5 Connection to Terminals
Both voltage and current outputs are floating, and in
the case of line operated units, may be connected to
the earth ground terminal on the front panel.
A voltage of the indicated polarity will be present
across the red and black
V
terminals. Be aware that
the specified voltage exists
right at the terminals
only.
If leads are used to bring this voltage to some
remote load, then a voltage drop develops across these
leads. Whether this drop is significant or not depends
on the amount of current flowing. If, for example,
the load is a high input impedance meter or other such
device, then the lead potential is safely ignored. If,
however, a large amount of current is drawn through
the connecting leads, then a significant drop may de-
velop across the leads and various contact resis-
tances. The user should be aware of this and note
the following procedures.
Whenever high currents are to be drawn, connec-
tions should be made with heavy cables and heavy
duty spade terminals or banana plugs securely attached
