Ac Voltage Measurement; Ac+Dc Measurement; Resistance Measurement; Ohms Connection - HP 3456A Operating And Service Manual

Model 3456A
voltages from lOO nanovolts through 1000 volts in five
ranges: 100 mV, I V, 1 0 V, 100 V, and
ranges are overload protected from input voitages up to
1000
V peak. The DCV input impedance is greater than
1010 ohms in the 100 mV to 10 V ranges and 10 M ohms
in the 100 V and 1 000 V ranges.
3-27. The measurement data can be displayed either as
Y2 , V I , V l , V I
a 6 5 4 or a 3 digit reading, depending on the
Number of Power Line Cycles Integrated (see
Paragraph 3-61) and the Number of Digits selected (see
Paragraph 3-63). Refer to Table 1-1 for accuracy
specifications.
3·28. AC Voltaga Maasurement.
3-29. The -hp- Model 3456A uses a True RMS conver­
tor and is able to measure voltages from 1 p.V to 700 V
RMS in four ranges: 1 V, 10 V, 100 V and 1 000 V. All
ranges are protected from input voJtages up to 1000 V
peak or 700 V RMS, whichever is less. Measurement
data can be displayed either as a 6
digit reading, depending on the selected Number of
Power Line Cycles Integrated (see Paragraph 3-61) and
the Number of Digits selected (see Paragraph 3-63). The
frequency response of the convertor is from 20 Hz to
250 kHz with a maximum input voltage of 1000 V peak
(700 V RMS, 1 ()8 VHz). The input impedance of the
convertor is 1 M ohms shunted by
Table 1-1 for accuracy specifications.
3·30. AC+DC Measurament.
3-3 1 . The AC+DC mode of the 3456A measures the
combined ac and dc components of the input signal and
displays its RMS value. Other operating characteristics
are the same as the ACV function. Refer to Table I-I
for accuracy specifications.
3-32. One use of the AC + DC function is to determine
RATIO REf
4IJR
i
OHMS
CURRENT
2·Wire Ohms Measurement
1000 All
V.
Yz , Y2, Y2 , Y2
5 4 or a 3
75 pF. Refer to
<
VOLTS
,WRn
n
SENSE
'WRn
GUARD
0
IQ]
0 0
Figure 3·5. Ohms Connection.
the necessary power rating of an amplifier. Since many
amplifiers have ac signals with dc components, the true
RMS value of those complex waveforms may need to be
+
known. The AC DC feature of the 3456A can simplify
these measurements since it can measure the RMS value
of the sum of the ac plus the dc voltage on the
waveform.
3·33. Resistance Measurement.
3-34. The Model 3456A is capable of measuring
resistance from 100 micro-ohm to I giga-ohm in eight
ranges. The ranges extend from the 100 ohm full scale to
the 1000 Meg-ohm full scale range. Resistance Measure­
ment can be made using either the 2-wire or the 4-wire
configuration. Refer to Figure 3-5 for the correct ohms
connection.
3-35. Resistance Measurements can be displayed as
V I , V I . Y2,
either a 6 5 or a 3
4
on the Number of Power Line Cycles Integrated (see
Paragraph 3-61) and the Number of Digits selected (see
Paragraph 3-63). The 4-WIRE ohm sense terminals are
protected to a maximum level of 350 V peak. Refer to
Table I-I for accuracy specifications.
3-36. The 3456A displays negative (minus) resistance
under two conditions:
a. The inputs to the 4 WIRE SENSE (RATIO REF)
or the 2WRO/4WRO (VOLTS) terminals are reversed
from each other in 4-wire ohms function.
b. Small negative voltages on measuring circuitry.
NOTE
With the measuring leads shorting or when
measuring small
be
readings may displa yed due to offsets in
the ohms circuitry.
R A T I O R E f
n
4IJR SENSE
i
O H M S
CURRENT
4-Wire Ohms Measurement
Operation
V I
digit reading, depending
resistances . negative
V O L T S
,WRn
'WRn
GUARD
o
3-5