3-28
IM DR231-01E
Power
supply
Example of a high-frequency
induction furnace
Inverter power supply
(20 to 3500kW)
Furnace
C
r
i
(0.2k to 10kHz)
Electrostatic
induction noise
Hot-line conduction
noise
Electro magnetic
induction noise
Electrostatic induction noise
Electro magnetic induction noise
Room
temperature
Line noise
The instrument
Temperature
inside
furnace
* Due to electromagnetic induction, current i flows
through the conductor, creating joule heat which
heats the furnace.
J=i
2
r
Φ
Power
supply
Inputs
Basics of Anti-Noise Measures (part 1)
Common Mode Noise and Normal Mode Noise
R
1
R
2
E
NM
H
L
Z
2
Z
1
E
CM
Z
3
i
2
i
1
E
O
+
E
ONM
Case
Circuit
common
Floating amp
Signal source
resistances
Normal mode noise
Signal
voltage E
Common mode noise
Signal component
Normal mode noise
component
Output
Common Mode Noise (E
CM
)
Noise generated between the signal source and the ground of a measuring instrument. Since it is
applied to both the H and L input terminals in phase with one another, it is also called in-phase
voltage.
Normal Mode Noise (E
NM
)
This is an unfavorable noise that is superimposed on a signal voltage. Since it is a voltage
between the H and L terminals, it is also called the line voltage, or since it is a voltage in series
with the signal voltage, it is sometimes called the series mode voltage.
3.8 Countering Noise
Summary of Contents for DR231
Page 12: ...10 IM DR231 01E...
