Section III
Model
3455A
Figure
3*2.
Ohmmeter Measurement
Connections.
volt full-scale to 1000 volts full-scale. Measurement
results are presented in
5-1/2
digits during normal
operation or in
6-1/2
digits when the 34S5A is set to the
High Resolution mode. All ranges except the 1000
volt
range have 50^ overrange capability and are overload
protected from input
voltages
up to ± 1000
volts.
Input
resistance
in the dc
function
is
greater than
10'^
ohms
on
the .1 V, 1 V, and 10 V ranges and equal to 10
megohms on the 100
V
and 1000 V ranges. Refer to
Table
1-1
for DC Accuracy specifications.
3-12. Rnistancs Maasuramant.
3-13.
The Model 3455A measures resistance from 1
milliohm to 15 megohms in six ranges extending from .1
kilohms ful scale
to 10.000 kilohms full scale. Measure-
ment results are presented in
5-1/2
digits during normal
operation or in ^1/2 digits when the 3455A is set
to
the
High Resolution mode. The only exception is that the .1
V range can only take a measurement in the
5-1/2
digit
mode. Resistance
may be measured in
“4-WIRE”
con-
figuration for optimum
accuracy or
“2-WlRE”
con-
figuration
may be selected for measurement conve-
nience. Figure
3-2
shows
proper connections for making
resistance measurements. The nominal
output
signal
current on the .1 kilohm, I kilohm and 100 kilohm
ranges
is
.7
mA. The nominal output current on the
1000 kilohm and 10,000 kilohm ranges
is
.7 microamp.
Maximum output voltage is limited
to
less than
5
volts
on all ranges. Refer to Table
1-1
for ohm accuracy
specifications.
3-14.
AC Voltage Meaiuremont.
volts
RMS.
Readings taken in the ac function are
display in the
5-1/2 digit mode only. Input impedance
of both
convertors is 2 megohms in parallel
with
< 75
pF for rear terminal input and <
90
pF for front
terminal input.
In addition
to
the normal ac volts func-
tion, the 3455A also has a fast ac volts function. The
fast ac function has a
faster
ac
reading rate than the nor-
mal
ac
function.
3-16.
The frequency response of the true RMS conver-
tor is from 30 Hz to 1 MHz in the normal ac volts func-
tion and from 300 Hz to 1 MHz in the fast ac
volts
func-
tion. Both ac signals
or
ac plus dc signals
(ac
signals
superimposed on a dc level) can be measured by the true
RMS
convertor.
Selection of the ac or ac -f dc inputs
are chosen
by
a switch located behind
the
rear
panels
reference cover. Refer
to
Table
1-1
for accuracy
specifications of each
ac
mode.
3-17.
The frequency response of the
average converter
is from 30 Hz to 250
Hz
in the
normal
ac
volts function
and
from 300 Hz
to
250 kHz in the fast ac volts func-
tion. Only ac signals (no dc component)
can
be
measured by the
average converter. Refer to Table
1-1
for
accuracy specification
of
each ac mode.
3-18.
In
order
to get accurate ac readings (especially
with
high voltage inputs at
high frequencies), the
low
in-
put terminal (front and rear) should
be
connected
to the
guard terminal
(front and rear). Refer to paragraph
3-39
for guarding information.
3-15.
The -hp- Model
3455A offers a choise of true
RMS (standard
unit) or
average
responding ac
conver- NOTE
tors (Option (X)l).
^th methods measure ac
voltages
from 10 microvolts
to
1000 volts
in four ranges exten- The front
pane! guard pushbutton applies
ding from 1 volt to 1(XX) volts ranges. All ranges, except
only for
front panel inputs. Be sure to
wire
the 1000 volts range, have
50%
overrange
capability and rear panel guard
connections yourself,
if
us-
are protected from input
voltage
components up
to
1000
ing the
rear pane! input terminals.
3-2
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