Kikusui TOS9301 - Page 31

TOS93 Series User’s Manual 31
Installation | Connection for Withstanding Voltage and Insulation Resistance Tests
Examples of how to connect test leads to the EUT
Reducing the effect of noise
Electronic devices in the surrounding area may malfunction due to the effect of noise produced by short
circuits across outputs or a dielectric breakdown of the EUT. To reduce the effect of noise, connect a
toroidal core or a resistor of approximately 470 Ω between the tips of the high- and low-voltage test leads
and the EUT.
Connect the toroidal core or resistor as close to the EUT as possible.
If you are connecting a toroidal core, it is effective to wrap the test leads two to three times around a type
of core that can be snapped on and that is often used with power cords. This type of core is usually
approximately 20 mm in diameter.
If you are connecting a resistor, pay close attention to the power rating of the resistor. When the upper limit
is 1
0 mA or less, connect a resistor of approximately 470 Ω (3 W, 30 kV impulse withstanding voltage).
Because connecting the resistor causes the voltage to fall, the voltage that is actually applied to the EUT is
slightly lower than the voltage that is generated from the product’s output terminals (when a 10 mA current
flows, the voltage falls approximately 10 V).
These methods are extremely useful in reducing the effect of noise.
To the HIGH
VOLTAGE
terminal
To the HIGH
VOLTAGE
terminal
To the LOW
terminal
To the HIGH
VOLTAGE
terminal
To the LOW
terminalTo the LOW
terminal
EUT EUTEUT
Ex: Between the power supply
(primary) and grounded
enclosure
Ex: Between the power supply
(primary) and ungrounded
enclosure
Ex: Between the insulation
connection area and
enclosure
470 ȍ, 3
W
470 ȍ, 3
W
Toroidal core
Toroidal core
HIGH VOLTAGE
LOW
TOS93TOS93
HIGH VOLTAGE
LOW
EUT
When connecting toroidal cores When connecting resistors
EUT