Keysight Technologies N432A, Руководство пользователя

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Operating Information 2
N432A User’s Guide 79
Precision power measurement
In this method, power is calculated using differential voltages (V
0
and V
1
)
obtained by measuring V
RF
and V
COMP
outputs with external digital
multimeters. This method helps to reduce measurement error to
±
(0.2%+0.5
μ
W).
To use this method, first you need to perform zeroing of the N432A and
measure its V
RF
and V
COMP
outputs using external digital multimeters.
These V
RF
and V
COMP
are equivalent to V
RF0
and V
COMP0
. From this, you
will obtain V
0
which is the difference between V
COMP0
and V
RF0
. Then, you
need to connect RF power to the thermistor sensor and measure the V
RF
and V
COMP
outputs again. These V
RF
and V
COMP
are now equivalent to
V
RF1
and V
COMP1
, which will give you a differential voltage of V
1
. Power
can then be computed by incorporating these values in the following
power equation:
where,
• V
COMP0
is the temperature compensation bridge top voltage measured
when zeroing is performed with the RF source disconnected
• V
COMP1
is the temperature compensation bridge top voltage measured
after zeroing with the RF source connected
•
V
0
= V
COMP0
– V
RF0
, without incident RF power
• V
1
= V
COMP1
– V
RF1
, with incident RF power
• R is the bridge resistance
•
ε
is the correction factor/effective efficiency
P
2 V
COMP 1
V
1
V
COMP 0
V
0
–
( )
V
0
2
V
1
2 –
+
4 R
ε
-----------------------------------------------------------------------------------------------------
=