Rms Value Of Ac Signals With Dc; Rms Current; Rms Ac-To-Dc Converter - HP 3400A Operating And Service Manual

Model 3400A
3-1. INTRODUCTION.
3-2. This section consists of instructions and infor­
mation necessary for the operation of the -hp- Model
3400A RMS Voltmeter.
fication of controls and indicators.
cedures, and operating instructions.
is a discussion of the applications for the Model
3400A.
3-3. CONTROLS AND INDICATORS.
3-4. Each operating control. connector, and indicator
located on the Model 3400A is identified and described
in Figure 3-1. The description of each component is
keyed to an illustration of that component which is
included within the figure.
3-S. TURN ON PROCEDURE.
3-6. To tur n o n the Model 3400A. proceed as follows:
a. Set 115/230 switch (7. Figure 3-1) to correct
position for input line voltage.
b. Apply ac voltage to Model 3400A by plugging
power cord into input power jack (8) ac receptacle.
c. Operate power switch (4) to ON; ensure that
LINE indicator (3) lights.
Allow five minutes for the Model
3400A to warm up and stabilize
before making a reading.
3-7. OPERATING INSTRUCTIONS.
DO NOT MEASURE SIGNAL ABOVE
80 VOLTS WITH 10 TO 1 CREST
FACTOR. OTHERWISE. THE MAXI­
MUM INPUT RATING ( 800 VOLTS
PEAK) WILL BE EXCEEDED. WHEN
MEASURING SIGNALS UP TO 80
VOLTS RMS WITH A 10 TO 1 CREST
FACTOR. USE THE BNC TO DUAL
BANANA JACK. ACCESSORY 1OUOA.
SUPPLIED WITH THE INSTRUMENT.
OR OTHER INPUT TEST LEADS AND
CONNECTIONS THAT WILL WITH­
STAND THE MAXIMUM INPUT OF
800 VOLTS PEAK.
3-8. To operate the Model 3400A as an rms volt­
meter proceed as follows:
a. Attach test lead to INPUT connector (6, Figure
3-1). (See Table 1-3 for a list oftest leads available. )
b. Set RANGE switch (5) to 300 VOLTS position.
SECTION
OPERATING
This section contains identi­
turn-on pro­
Also included
III
INSTRUCTIONS
WHEN MEASURING AN AC SIGNAL
SUPERIMPOSED ON A DC LEVEL.
ALWAYS SET THE RANGE SWITCH
TO THE 300 VOLT POSITION.
A HIGH VOLTAGE TRANSIENT DUE
TO THE APPLICATION OF A DC
VOLTAGE WILL DAMAGE THE
INPUT CIRCUITRY.
c. Connect test lead to point to be measured.
(l)
d. Rotate RANGE switch counterclockwise until
meter indicates on upper two thirds of scale.
3-9. APPLICATIONS.
3-10. The Model 3400A can be used in conjunction
with other test instruments to measure the rms
value of ac signal with a dc component, measure rms
current and act as an rms ac-to-dc converter.
additional information on special applications. contact
your -hp- Sales and Service Office.
3-11.

RMS VALUE OF AC SIGNALS WITH DC

COMPONENT.
3-12. Since the 3400A is an ac device it will measure
only the rms value of the ac component.
essary to include the rms value of the dc component
when measuring a signal use a -hp-Model 412A DC
Voltmeter to measure the dc component.
the reading from the Model 412A and Model 3400A in
the following formula:
may be superimposed on a dc level of up to 600 V.
e
rms
3-13.

RMS CURRENT.

3-14. To measure rms current. use an-hp- Model 456A
AC Current Probe.
current conductor and provides an output voltage that
is proportional to the current being measured. Using
this method. rms currents of one milliampere to one
ampere can be measured.
3-15.

RMS AC-TO-DC CONVERTER.

3-16. Since the Model 3400A is provided with a dc
output (10. Figure 3-1) which is proportional to the
meter deflection, it can be used as a linear rms ac
to de converter. The dc output can be used to drive a
-hp- Model 3440A Digital Voltmeter for high resolu­
tion measurements and/or a Mosely Model 680 Strip
Chart Recorder. External loading does not affect the
meter accuracy so that both the meter and dc output
can be used simultaneously.
may be purchased under -hp- Part No. 1251-0067.
Section
H
it is nec­
Substitute
The ac signal (up to 800V peak)
2 2
+
e
ac dc
This probe clips around
A plug for DC OUT jack
ill
For
the
3-1