Shift Operltion; Ratio - HP 3456A Operating And Service Manual

Digital voltmeter
Hide thumbs Also See for 3456A:
Table of Contents

Advertisement

Operation
NOTE
The 3456A's Analog Filter (see Paragraph
be
3-52) should not
functions. The filter is disabled when the
ohms f unctions are selected f rom the f ront
panel.
3·37. Shift Operltion.
3-38. The purpose of the SHIfT button is to place the
3456A in the Shifted Functions. To disable the shifted
functions, press the SHIfT button aga in. The SHIfT
button'S color is green and corresponds to the green let­
tering and symbols above the function buttons to iden­
tify shifted functions. All shifted functions readings are
made by taking multiple measurements.
NOTE
The 3456A ' s Autozero f eature (see Para­
graph 3-48) is automatical l y enabled in f ront
panel selectable shifted functions.
3-39. Rltio.
3-40. The
-hp-
Model
OCV IDCV, ACV IDCV, or ACV + DCV IDCV Ratio
Measurements. This is done by taking a Signal,
Reference High, and Reference Low Voltage reading
which are all referenced to a common point, the VOLTS
LOW terminal. The Signal Voltage is measured from
the VOLTS HIGH terminal to the VOLTS LOW com­
mon. The Reference High Voltage is measured from the
RATIO REF HIGH terminal to VOLTS LOW and the
Reference Low Voltage is from the RATIO REF LOW
terminal and VOLTS LOW. Refer to Figure 3-6 for a
typical Ratio Measurement. Select the Ratio functions
using the DCV, ACV, ACV + DCV function buttons in
the shifted mode (press the SHIfT bunon). The green
symbols above the function buttons identify the Ratio
functions. Refer to Table 1-1 for accuracy specifica­
tions.
RflTJO REF
4WRll SENSE
Figure 3·6. Rltio Connection.
3·6
used with any ohms
3456A can
either make
VOLTS
'"''''
'WAA
GUflRO
IQ]
0
H56-3-6
a. Ratio Formula. A Ratio Measurement is a
mathematical operation expressed in this formula:

Ratio

=
Reference Voltage
The 3456A Ratio Measurement formula is:
Ratio
=
Reference High - Reference Low
Remember, the three voltages are referenced to the
VOLTS LOW terminal. The Reference Low voltage
should be kept low for an accurate Ratio measurement
± 90/0
(within
of Reference High Voltage). The voltage
can be kept low by shorting or otherwise connecting the
RATIO REF LOW and VOLTS LOW terminals to each
other, either at the terminals or measuring point.
NOTE
For a three wire Ratio Measurement connect
the REFERENCE LOW and VOL TS LOW
terminals to each other.
b. Ratio Measurement. For a Ratio Measurement the
Reference Voltage can be between 0 to
12 V level is the maximum Reference Voltage level the
instrument is able to measure (the RATIO REF ter­
minals are protected up to 350 V peak). The Signal
Voltage, which is applied at the VOLTS terminals. can
either be dc, ac, or ac+dc volts from 0 to
or 700 V RMS. In addition, the Analog Filter (see Para­
graph 3-52) and Delay (see Paragraph 3-67) are not used
for the Reference Measurement. These features can be
selected for the Signal Voltage Measurement. The
following is a typical Ratio Measurement procedure.
1 . Measure your Signal and Reference Voltages and
make sure they are within the range for a Ratio
Measurement (refer to Table 1 - 1 for the limits).
Use the instrument's unshifted functions for those
measurements.
2. Connect the Reference Voltage between the HIGH
and LOW REFERENCE terminals.
3. Connect the Signal Voltage between the HIGH
and LOW VOLTS terminals and connect RATIO
REF LOW to VOLTS LOW.
4. Set the 3456A to the desired range or to
Autorange.
5 . Place the instrument into the Ratio mode by press­
ing
the
appropriate
ACV IDCV, or ACV + DCV IDCV in the shifted
mode).
6. Read the Ratio reading on the display.
Model 3456A
Signal Voltage
Signal Voltage
12 V dc. The
±
l()()()
V peak
button
(DCV IDCV,
")

Hide quick links:

Advertisement

Table of Contents
loading

Table of Contents