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Appendix
Appendix
Appx. 1 RMS and Average
Difference between the RMS and Average
When converting AC to RMS, 2 methods are available, “True RMS method (True RMS indication)” and “Average method (Average rectifying RMS indication)”.
In the case of the sine wave where no skew is included, the same values are indicated in both methods. However, if the waveform is skewed, a difference occurs between the 2 methods.
The true RMS method is applied to this instrument.
In the true RMS method, the high frequency component is also included and displayed.
In the average method, the input waveform is handled as a sine wave where no skew is included (only single frequency). The average of the AC signal is obtained, converted to the RMS, and then displayed. If the waveform is skewed, a greater measurement error occurs.
Measurement example
100 V sine wave
100 V square wave
True RMS
100 V
100 V
Average rectifying
100 V
111 V
V(t) V(t)
1
2
3
4
5
6
7
Vm Vavg Vrms t
Vm=Vavg=Vrms t
T
Sine wave
T
Square wave
Vm: Maximum value, Vavg: Average value, Vrms: RMS, T: Time period
正弦波
方形波
Appx.
1
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DC+AC の波形
DC 成分の波形
AC 成分の波形
DC+AC の波形
DC 成分の波形
114.1V
1
2
3
85.9V
100V
Operation Example
114.1V
85.9V
100V 100V
±14.1V
Appx. 2 Operation Example
Checking the noise of the DC voltage
Measure the AC component voltage, DC component voltage, and peak value.
4
5
6
DC+AC の波形
114.1V
85.9V
100V
Synthesized components of AC and DC
DC
8
Black
Red AC 成分の波形
9
DC+AC
Synthesized voltage of AC and DC
114.1V
85.9V
100V
DC component
100V
AC component
±14.1V
DC+AC
1
DC component voltage
2
DC 成分の波形
85.9V
100V
100V
114.1V
±14.1V
85.9V
100V
AC 成分の波形
DC+AC
DC/AC
Peak voltage
±14.1V
100V
AC 成分の波形
±14.1V
DC/AC
PEAK
PEAK
Appx.
2
3
100V
±14.1V
4
5
6
7
8
9
10
PEAK
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Capacitor Capacity Measurement Principle
Appx. 3 Capacitor Capacity
Measurement Principle
The instrument measures the capacity using the CR self-excited oscillation method (triangle wave).
R: Instrument internal circuit Varies with each range.
C: Object to be measured Capacitor
When the capacitor to be measured is connected, self-excited oscillation begins. The capacity is calculated based on the measured frequency during self-excited oscillation. The frequencies during self-excited oscillation are shown in the table below.
Measurement range
1 nF
10 nF
100 nF
1 µF
10 µF
100 µF
1 mF
10 mF
100 mF
Resistance of the instrument internal circuit
100 k Ω
100 k Ω
100 k Ω
100 k Ω
5 k Ω
5 k Ω
5 k Ω
5 k Ω
5 k Ω
Reference oscillation frequency
500 Hz to 600 Hz
300 Hz to 600 Hz
60 Hz to 600 Hz
6 Hz to 600 Hz
15 Hz to 5100 Hz
1.5 Hz to 5100 Hz
5 Hz to 9300 Hz
0.5 Hz to 9300 Hz
0.05 Hz to 9300 Hz
1
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3
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7
Even when the same capacitor is measured, the capacity may vary depending on the measurement range. This is because the oscillation frequency is different even in the same capacitor since the resistance R of the instrument internal circuit changes for each measurement range.
Consequently, the capacity differs as shown in the table below depending on the measurement range when a measurement target that is frequencydependent, such as an electrolytic capacitor, is measured. The table shows the capacity for each frequency and contains true values.
Appx.
3
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Dedicated Software (DMM Communicator)
(Example) Measurement of 100 µF electrolytic capacitor
Measurement range Oscillation frequency Instrument displayed value
100 µF
1 mF
1.369 Hz
50.797 Hz
101.9 µF
0.090 mF
Appx. 4 Dedicated Software
(DMM Communicator)
The PC application (DMM Communicator) can be used to send measurement data from the instrument to a computer or to configure instrument settings from a computer.
The DT4900-01 Communication Package (USB) dedicated communications adapter is required in order to connect the instrument to a computer.
Specifications
• Display, record, and graph measurement data from the instrument
• Configure instrument settings such as the range
• Display a connection screen based on the instrument’s measurement function
• Save recorded measurement data as a CSV-format text file
• Paste measurement data into Excel ®
• Load DMM instrument memory data
Microsoft Excel is a registered trademark of Microsoft Corporation in the
United States and other countries.
Appx.
4
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16-01 EN
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