Measurement; Ac Voltage Measurement - HP 3455A Operating And Service Manual

Section III
Model 3455A
4.WIRE MEASUREMENT
INPUT
(2 WIRE )
GUARD QSIGNAL
{4 WIRE)
SIGNAL
CURRENT Rx
2-WIRE MEASUREMENT
GUARD
QSIGNAL tNPUT
(2 WIRE)
(4 WIRE)
SIGNAL
CURRENT
3455-B-4667
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 3455A 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 de function is greater than 10!9 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. Resistance Measurement.
3-13. The Model 3455A measures resistance from |
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 6-1/2 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-WIRE'' 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, 1 kilohm and 10 kilohm ranges
is .7 mA. The nominal output current on the 1000
kilohm and 10,000 kilohm ranges is .7 microamp. Max-
imum output voltage is limited to less than 5 volts on all
ranges. Refer to Table 1-1 for ohm accuracy specifica-
tions.
3-14. AC Voltage Measurement.
3-15. The -hp- Model 3455A offers a choise of true
RMS (standard unit) or average responding ac conver-
tors (Option 001). Both methods measure ac voltages
from 10 microvolts to 1000 volts in four ranges exten-
ding from 1 volt to 1000 volts ranges. All ranges, except
the 1000 volts range, have 50% overrange capability and
are protected from input voltage components up to 1000
3-2 RevA
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 + 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. .
NOTE
The front panel guard pushbutton applies
only for front panel inputs. Be sure to wire
rear panel guard connections yourself, if us-
ing the rear panel input terminals.