Rear Input; A Only) Iv 2 Digits (1071 Only) - Datron 1061A User Handbook Manual

Rear
input
The measurement source
may
be
connected
to
the
'REAR
I/P'
plug instead
of the front panel
terminals
when
the 'I/P
SELECT
rear
panel
switch
is
set
to the
'REAR'
position.
For
all
rear
panel inputs, the
maximum
limit
is
250
V RMS.
When
using the rear
panel input plug the front
panel
switches '4-wire
ft /
2-wire
ft'
and
'Local
Guard
/
Remote Guard' are inoperative.
Therefore
to effect
local
guarding, a connection
should always
be
made
between 'Guard' (pin
H) and "Ohms
Guard' (pin A).
For
2-wire resistance
measurement
external connections
must be
made from
'Hi'
to
T+'
and
from
"Lo' to 'I—'.
Fig. 2.2
Rear
input
7
pin plug
Thermal
EMF
Thermal
emfs
are significant in
DC
voltage,
current
and
resistance
measurements,
especially
when
measuring low voltages or large currents.
These
unpredictable
thermal
emf
errors arise
when
dissimilar
metal
junctions are
at
different
temp-
eratures.
To
minimise thermal
emf
errors use the
same
material
throughout
the
measuring
circuit,
particularly
avoid the use of
steel
probes,
nickel
plated terminals
and
tinned
copper
wire.
The
table
below shows thermal emfs
relative to
hard
drawn
copper
at
23° C.
MATERIAL EMF
gV/°C
SILVER
+0.03
GOLD
+0.01
TIN
-3
LEAD
-3
NICKEL
-22
If
dissimilar
metal junctions are
used ensure
that
they are
offset
by other junctions of the
same
material
at
the
same temperature and allow
for
thermal emfs
by making
the
measurement
twice
with reversed polarities.
A
lead
with gold plated
copper
terminals
is
provided
in
the
Datron
lead
kit
for
making
low thermal
emf
connections.
6
V
2
Digits
(1061
A
only)
7Vt
Digits
(1071 only)
terminals
(1071
:
7V2
digits)
On
the 1061
A
and
1071
models
only, selection
of
'Input
filter'
extends the
DC
Voltage
and
Resistance
displays
by an
extra
digit:
i.e.
1061
A
is
extended
to
6 1
/2
digits.
1071
is
extended
to IVi digits.
If
option
12
is
fitted
in 1061 A.
then 'Input
Filter'
also
selects
6
V
2
digits for
'AC
and
"DC Coupled AC'
functions.
De-selection of
this
feature
is
achieved by
re-pressing
the 'Input
filter'
key.
Refer
also to
'Average
Mode
measurements'
in
Section
3.
2-9