Ac Voltage Measurement - Datron 1061A User Handbook Manual

AC
voltage
measurement
procedure
terminals
below
360Hz
{1061
A
with
Option 12: 6Vz digits)
DC
coupled
AC
voltage
measurement
procedure
{1061
A
with
Option
12:
6Va
digits)
AC
voltage
measurement
Whereas
for
DC
voltage
measurement the resistance
of
the
connection lead
is
generally
unimportant so
long as
it is
small
compared
with the
input
impedance
of
the
measuring device,
with
AC
voltage
measurement
the capacitance
may
give rise
to
an
appreciable shunting effect
causing source
loading as
well as
voltage
drop in the leads.
The
approximate
'Hi'
to 'Lo'
capacitance of
the leads in
the
Datron
lead kit are,
low thermal
emf
lead
with
spade terminals:
—
65pF, other
leads:
—
160pF. In
extreme
cases,
use
of separate leads will
give
lower capacitance (dependent
upon
spacing but
typically
4pF) but
will
be
liable
to
corrupt the
measurement
by adding induced signals.
The
table
below
gives the
approximate
impedances
at
different frequencies.
FREQUENCY
LEAD CAPACITANCE
4pF
65pF
160pF
100Hz
400Mf2
20M£2
iowa
1kHz
40M£2
2Mf2
iMa
10kHz
4Mft
200kfi
iooka
100kHz 400k£2
2 0kf2
ioka
1MHz
40kf2
2kH ika
Table
2.4
Connection lead
capacitance
2-5