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Chapter 7 Basic Principles and Technical Specifications
7.1 Basic principles
System principle and functional block diagram, as shown in Figure 7-1:
(Figure 7-1 System Structure)
The main structure of the JK9306 series single-phase power meter is to input the voltage and
current of the equipment under test through the instrument to the instrument through
differential input. Through the instrument's internal amplification, filtering, sampling, and AD
conversion, the analog signals of voltage and current are synchronized and sampled. It is
converted into digital quantities Ui and Ii, and then the CPU uses discrete integration to obtain
the voltage effective value, current effective value, active power, and power factor according to
the following formula and sends them to the liquid crystal display. Because the calculation of the
effective value includes the AC component And DC components, and the AC waveform may
become a non-standard waveform due to partial distortion, so the rms calculations here are true
rms values, that is, true rms values. The calculated power also includes the AC and DC
components of the voltage and current. Therefore, the power calculation belongs to the average
power and is also the real power value, that is, the active power. The sign of the power
represents the flow of power (respectively whether the power provided by the power supply to
the load or The energy provided by the load to the power supply). The power factor is the ratio of
the active power to the apparent power (total power). Theoretically, there is no sign of the power
factor. However, in the application of the power meter, the sign of the phase relationship
between voltage and current is determined by the sign of -1. Between ~ + 1, a positive value
represents the voltage leading current and a negative sign represents the voltage lagging current.
In addition to the RMS test mode, this series of instruments also provide AC and DC test modes.
If the input source includes AC and DC components, you can switch modes to view the
corresponding AC and DC components, respectively.
For harmonics, some instrument models do not have a harmonic analysis function, and
instruments with a harmonic analysis function are for power frequency power signals (50 / 60Hz),
and for harmonic results of non-power frequency signals, this series of instruments can View but
no precision indicator. This series of instruments provide optional opening of the 5kHz filter. This
filter is not suitable for non-power frequency power supply and needs to be manually turned off
(optional in the measurement settings). The harmonic order that can be analyzed and viewed is 2
~ 50 times.
