Adjustments 3
E4416A/E4417A Power Meters Service Guide 67
by using the following assumptions:
The error in doing this is:
So if , that is, then the error can be
ignored. In practice and . The eror is less than
0.01%.
By substituting equation 3 into equation 1 and manipulating the result you get:
This quadratic can be solved to give equation 2.
The definitions of the terms in equation 2 are:
• V
0
is the voltage measured between V
comp
and V
RF
with no power applied
and after the Agilent 432A has been zeroed.
• V
1
is the voltage measured between V
comp
and V
RF
with power applied. This
power is approximately 1 mW.
• V
comp
is the voltage between the Agilent 432A V
comp
connector and chassis
ground with power applied.
• R is the resistance of the mount resistor in the Agilent 432A power meter
• Calibration Factor is the value of the thermistor mount at 50 MHz.
Equipment
• Test power meter: Agilent 432A.
• Thermistor Mount: Agilent 478A Option H75 or H76.
• Digital Voltmeter (DVM): Agilent 3458A.
V
1
2
V
0
2
2V
1
V
0
–+()– V
0
2
V
1
2
–()–2V
0
2
–2V
1
V
0
+2V
0
V
1
V
0
–()==
0 V
1
V
0
–()
2
2V
com p
V
1
V
0
–()–410
3–
()R CalibrationFactor()+=
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