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STB6684/A Operation Manual
After the measurement the capacity has to be discharged. In STB6684/STB6684A, this is done by
switching the output to a 2kΩ/5W wire wound resistor. The stored energy in a capacitor is
calculated from:
At 500V this limits the capacity that can be discharged by the internal resistor to 4mF. The
discharge time can be found from:
T
= R
.C.ln(U
disch
disch
Example: R
= 2kohm,
disch
t disch = 36 sec!
If larger energies than specified here have to be discharged or if the discharge time must be
shortened, it must be done with an external resistor.
Range selection of STB6684/ STB6684A:
Range 1: 10OuA – 1mA;
Range 2: 10uA – 100uA;
Range 3: 1uA – 10uA;
Range 4: 100nA – 1uA ;
Range 5: 10nA – 100nA;
Range 6: 1nA – 10nA ;
Range 7: 10pA – 1nA ;
The correct range is established from measuring the leakage current on several known good and
known bad components at the specified voltage and charge/dwell/soak time. The range to choose is
the most sensitive range that do not lead to overflow at the upper limit of the leakage current. The
upper limit is established from the measure voltage divided with the minimum insultaion
resistance:
L
= U
/ IR
Limit
HT
For example: U
= 100V, IR
HT
6.7 Examples for sequence test
Example 1: 20 sec. Measure to Go
STEP FUNCTION
1
CHARGE
2
WAIT
3
MEAS. TO GO
4
DISHCHAGE
5
/ U
)
start
finish
C = 4mF,
U
start
min
= 25Gohm => I
min
HV(V)
RANG
500
N/A
500
N/A
AU _H
◇ 84
Chapter 6 Measurement Procedures and Examples
(3)
(4)
= 500V,
U
= 5V :
finish
= 4 nA, select range 6.
leak,max
AVG
LOW
N/A
N/A
N/A
N/A
4
500Gohm
HIGH
TIME
N/A
1.0s
N/A
1.0s
18.0s
2.0s
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