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Programming
of
Operational Functions
OUTPUT
ON/OFF
The
analog
OUTPUT
is
switched
off
by
command
00
(output
disable),
and
switched
on
to
the selected
value
by
01.
The
amplitude
and
frequency of
the
output
are
derived
from
the
'M'
code and
'H'
code
data
used
to set
the
'Main'
(OUTPUT
display),
and
'Auxiliary'
(MODE/FREQUENCY
display) reg-
isters.
Safety Delay
The
High
Voltage
Safety
delay
(3
seconds)
is
nonnally
active
(D0).
It
can be
overridden
by
the
command
Dl,
but
the
use of
this
command
sets
up
potentially
dangerous
situations.
D0
is
enforced
by any
Function
or
Range
change
(including
Au-
torange changes).
WARNING:
DO NOT
USE
Dl
UNLESS
IT
IS
ESSENTIAL
FOR
fflGH
SPEED OPERATION.
TAKE
SAFETY
PRECAUTIONS
TO PROTECT PERSONNEL
IN
THE
VICINITY.
Function
F0
(DC
voltage),
FI
(AC
voltage),
F2
(DC
Current),
F3 (AC
Current)
and
F4
(Resistance) configure the instrument
to the
required
function.
Output
Range
R
1
through
to
R9
configure
the
4708
to specific
ranges as
shown
earlier in
Table
5.4.
R0
puts the instrument
in
auto-range
function,
allowing
the
output value
to
be
specified as
a
number
without
setting
the actual range.
Ranging
down
occurs
at
20%
of
range,
i.e.
Full Scale value
of next lower
range.
Ranging up
occurs
at
Full Scale. In autorange,
commands A0, A1
and
A2
are
invalid.
Output
Display
Value (Main
Register)
In
remote programming,
the
incremental
1 4 method
of
setting
the
output value
is
not used.
Instead,
Code
M±***
is
used
to set
the
output value
explicitly, either in
numeric,
scientific
or
engineering
notation (see
examples
below).
If
the resolution
is
too high, the value
is
truncated
to
the correct resolution
and
the
controller
is
informed
by
SRQ
and
RQS
Status
byte
(see
RQS
status
byte formats
later in this
section).
High Voltage Outputs
The
change
fi'om
Low
to
High
voltage
state
is
controlled
by
the
same
interlocks
which govern
the
manual changeover
(Refer
to
Section
4,
page
4-7).
To
effect
the
changeover,
the
command
string:
'M
(followed
by
voltage)
01
='
should
be
used
if
OUTPUT
is
already
on and
a range change
is
not involved.
If
a range
change
is
programmed
to set
the output
into
high
voltage
state (for
instance
in
R0)
the '01'
should be
sent as
a
separate
string.
If
the
M
code
alone
is
attempted
(M*'"'''...=)
with
OUTPUT
already
enabled
(01),
the
new
value
is
set in
the
Main
Register
(OUTPUT
display);
but
the
output voltage
will
not
ramp
to
high
voltage
state until
the
enabling
string
'01 ='
is
received.
If
the
attempt
had been
made
with
OUTPUT
disabled (00), the
01 would be
required
in
any
case.
It
should
also
be
remembered
that
the output
circuitry
needs time
to
settle
to
its
final
value, especially
if
a range-change
is
incurred.
Delays should be
included
in
the controller
program
to
allow
for
this.
During
these processes, the
fi'ont
panel warnings of
flashing
LEDs
and
pulsing tones operate as
for
manual
operation.
Nevertheless, access
to
the front
panel should be
restricted
because
the
high speed of
programming
in
the
IEEE
inter-
face
adds
to the safety
hazard.
Examples
of
valid
M
codes:
Required
Output Value
Function
Range
M
Code
Output
Display
-153V
F0
R7
M-153
-153.000,0V
+1.621257V
F0
R5
M+1.6212574
-h1.621,2574V
1.621257V
RMS
FI
R5
M1621257E-6
1.621,257V
~
1.621257V
RMS
FI
R0
M1621.257E-03
1.621
,257V
~
(Autorange
to
R5 =
1
V)
0.002563
RMS
F3
R0
M.002563
2.56300mA ~
(Autorange
to
R3 = 10mA)
5-8
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