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In the BIT test process, the data that from the single test point or once test can't
ensure the accuracy and integrality of the test, for the test result can only reveal the
situation of the test object partly and be influenced by all kinds of noise easily. The test
data got by many test point can reduce the influence of noise and reveal the actual
situation of system, reduce the fault rate of BIT circuit mostly.
Suppose the false alarm rate of BIT circuit fault produced by single test point
P
is
the final false alarm rate of BIT circuit fault. Taking the minimum false alarm rate of
the BIT circuit as the optimized objective, the optimized formula is as follow:
P
(
m
λ
)
(
λ
)
is
, satisfied (0, 1) distribution and each of the test points is separate.
P
(
λ
)
P
( λ
)
P
(
2
λ
)
P
(
m
λ
)
=
(3)
…
m: The maximal number of the test point in BIT circuit.
It can obtain from formula (3) that m is inversely proportional to
. So the more
P
(
λ
)
test point the lower false alarm rate produced by BIT circuit fault.
Formula (3 can be express as follow:
P
(
K
)
P
(
K
)
P
(
K
)
P
(
K
)
=
(4)
…
m
1
2
m
The maximal number of the test point in BIT circuit.
the false alarm rate of BIT circuit.
P
(
K
)
P
(
K
)
the false alarm rate of single test point in BIT circuit.
m
P
(
K
)
P
(
K
)
Because
<1, it can be obtain by formula (4) that
is inversely
m
proportional to m, the lager m is, the false alarm rate is lower.
So the more test point designed in the system, the higher rate of fault test and fault
isolation is. The system is more reliability. But the BIT test system need realized by
special hardware circuit, so the more BIT test system induce the totality system is more
complex. The totality system is less reliability and bigger cubage. So the number of BIT
test system or the value of m should not be raised, when the rate of fault test, fault
isolate and false alarm is satisfied the system demand. The number of BIT test system
designed in this paper is less or equal to 3, and the data from different test point should
be information fusion for improve test validity and reduce the conflict of the data from
different test point.
It can be get from formula (4 that reducing m can raise false alarm rate, raising m
can reduce false alarm rate. When raising m, the system will be more complex, weight,
bigger, and less reliability. The conflict can be resolve by analyzing formula (4),
)
P
(
K
)
P
(
K
)
P
(
K
P
(
K
)
is proportionate to
. When m is definite, reducing
,
is
m
m
P
(
K
)
decreased too. For
<1, formula (5) can be got as follow
m
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