HP 400D Operating And Servicing Manual page 13

EFFECT OF HARMONICS ON MODEL
TABLE 2-1.
Input Voltage Characteristics
Fundamental
=
Fundamental +10% 2nd harmonic
Fundamental +20% 2nd harmonic
Fundamental +50% 2nd harmonic
Fundamental +10% 3rd harmonic
Fundamental + 2 0% 3rd harmonic
Fundamental +50% 3rd harmonic
ith the instrument plugged into a power
source of specified voltage and frequency, and the
toggle switch at ON, allow the instrument about
five minutes t o reach a state of stable operation.
2) Set the DB VOLTS (range) switch to the desired
voltage range.
3) Connect the voltage being measured to the
binding posts.
4) The value of voltage being measured will be
indicated on one of two scales:
O-to-3 volts. W h e n the range used contains the
integer "1", the value of the voltage being measured
will be indicated. on the I-volt scale: when the range
used contains the integer "3", the value of the volt­
age will be indicated on the 3-volt scale.
range switch position shows the maximum voltage
that can be measured on the appropriate meter scale.
,
CAUTION
When making power line voltage measurements with
this
instrument you must be careful to avoid a serious
short circuit. Connect only the red input terminal
to the side of the power line that produces approxi­
mately the correct indication
connect the black terminal to the other side of the
line. By following this procedure you will avoid
the short circuit that would result from connecting
the black input terminal which is grounded to the
ungrounded side of the power line.
b.
in the same way as voltage measurements except
that the indication is read on the db scale (-12 t o
100
INPUT
O-to-l volt or
Each
on
the meter and then
of decibels are made
400D/H/L VOLTAGE MEASUREMENTS
True
RMS Value
100
100.5
102
112
100.5
102
112
+2 decibels). The level in decibels is the algebraic
sum of the meter db-scale indication and the DB
VOLTS (range) switch position.
1) To read power directly in dbm
watt into 600 ohms), the measurement must be made
across 600 ohms.
2) Comparative db measurements (without respect
to the reference level) may be obtained by direct
reading provided each measurement is made across
of
the impedance.
same value
the difference in decibels between two or more
measurements may be obtained directly from the
db-scale indications.
3) To obtain the level in dbm with respect to im­
pedances other than 600 ohms, the meter correction
in
graph shown Figure 2-1 may be used.
in dbm will be the algebraic sum of the level as in­
dicated on the meter and the correction shown on the
U
graph. For example,
+30 db pOSition, the measurement made across
and
90 ohms, the indication
+1, the level in dbm is obtained as follows:
+ 1 (db scale indication)
+30 (range switch position)
'ill
(level in db as indicated by meter)
+ 8 (correction for 90 ohms impedance)
+3'9"
dbm
For the same conditions, with the measurement
60,000
made across ohms:
1
+ (db scale indication)
+30 (range switch position)
ill in
(level db as indicated by meter)
-20 (correction for 60,000 ohms impedance)
ill
dbm
Sect. Il Page 3
Value Indicated
by
400D/H/L
Model
100
100
100-102
100-110
96-104
94-108
90-116
1
(O rlbm milli­
=
Madc
in this manner,
The level
the range switch is at the
on
the DECIBELS scale