Omega 868F, Руководство пользователя

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10
4.2.2 Signal Phase
During the signal phase the 4 charged values of voltage are
transfered to other parts of the circuit (refer to simplified Figure 4-4).
The following explanations assume more than one charge transfer has
taken place.
1. C
R
is connected across C
E
and after a sufficient number of
zero and signal phases the voltage on C
E
approaches that
stored on C
R
. That voltage is equal to IR
R
.
2. C
Z
is connected between L
2
and the input of A
1
in a way that
opposes the voltage drop across R
T
and L
4
. Since the voltage
charged on C
Z
is IR
Z
the voltage at the output of A
1
is
[A
1
(I(R
T
+ L
4
) - IR
Z
+ Vos)]
or
A
1
(I(R
T
- R
Z
+ L
4
) + IR
Z
+ Vos)
R
Z
is made to equal the value of R
T
at 0°C. This action
eliminates the offset of R
T
(100Ω at 0°C).
3. C
D
is connected between the output of A
1
and the top of C
D
in such a way that opposes the output of A
1
. The voltage
charge on C
D
is
A
1
(I(R
T
- R
Z
+ L
4
) + Vos) - A
1
(IL
4
+ Vos)
or
A
1
I(R
T
- R
Z
)
4. C
A
is connected between the output of the A
2
network and
the top of C
B
in such a way that opposes the output of A
2
.
The voltage charged on C
B
is
A
1
A
2
(I(R
T
- R
Z
+ L
4
) + Vos) - A
1
A
2
(IL
4
+ Vos)
or
A
1
A
2
I(R
T
- R
Z
)
Due to this two phase measurement Vos and lead resistance
effects are eliminated.
Figure 4-4. Four Wire Signal Phase