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HT9020
EN - 4
2. GENERAL DESCRIPTION
The HT9020 instrument carries out the following measurements:
DC and AC+DC TRMS voltage
DC and AC+CD TRMS current
Phase sequence and conformity test
AC powers and power factor on single-phase and/or balanced three phase systems
AC energies on single-phase and/or balanced three-phase systems
DC
power
AC voltage harmonics up to 25° order and THD%
AC current harmonics up to 25° order and THD%
Frequency on voltage (with test leads) and current (with clamp jaw)
Resistance and continuity test
Electric motor starting currents (Dynamic Inrush)
Detection of AC voltage with and without contact with built-in sensor
Each of these functions can be selected using the 6-position selector switch, including
OFF position. Keys
F1
,
F2
,
F3
,
F4/OK
and
H / ESC /
are also provided. For their use,
please refer to § 4.2.
2.1. MEASURING
AVERAGE
VALUES AND TRMS VALUES
Measuring instruments of alternating quantities are divided into two big families:
AVERAGE-VALUE meters: instruments measuring the value of the single wave signals
TRMS (True Root Mean Square) VALUE meters: instruments measuring the TRMS
value of the quantity being tested
In the presence of a perfectly sinusoidal wave, both families of instruments provide
identical results. In the presence of distorted waves, on the other hand, the readings shall
differ. Average-value meters provide the RMS value of the sole fundamental wave, TRSM
meters, instead, provide the RMS value of the whole wave, including harmonics (within the
instrument’s bandwidth)
2.2.
DEFINITION OF TRUE ROOT MEAN SQUARE VALUE AND CREST FACTOR
The root mean square value of current is defined as follows: "
In a time equal to a period,
an alternating current with a root mean square value of the intensity of 1A, circulating on a
resistor, dissipates the same energy as that which would have been dissipated by a direct
current with the intensity of 1 A during the same time
". This definition results in the
numeric expression:
G=
T
t
t
dt
t
g
T
0
0
)
(
1
2
The
root mean square value
is indicated with the acronym RMS. The
Crest Factor is defined as the relationship between the Peak Value of a signal and its RMS
value: CF (G)=
RMS
p
G
G
This value changes with the signal waveform, for a purely sinusoidal
wave it is
2
=1.41. In case of distortion, the Crest Factor takes higher values as wave
distortion increases.
Summary of Contents for HT9020
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