Boonton 4240 RF Power Meter - Manual (Page 113)

Boonton 4240 Series RF Power Meter
6.2 M
The 424
Standard year
calibratio
chapter assumes that the power meter is being maintained correctly and is within its valid calibration period.
Measure
and the
mathema
error is obtained by combining the linear
(percent) ources in cu take into account the statistical
shape of e expe
Note tha ed given in either percent or dB. The following
formulas ay be
U
%
Section 6.2.1 outlines all the parameters that contribute to the power measurement uncertainty followed by a discussion on
the method and calculations used to express the uncertainty.
Section
Section 6. sors with complete
Uncertai y Budg
6.2.1 Uncertainty
The total measurem s:
easurement Accuracy
0 Series includes a precision, internal, 50 MHz RF reference calibrator that is traceable to the National Institute for
s and Technology (NIST). When the instrument is maintained according to the factory recommended one
n cycle, the calibrator enables you to make highly precise measurements of CW signals. The error analyses in this
ment uncertainties are attributable to the instrument, calibrator, sensor, and impedance mismatch between the sensor
device under test (DUT). Individual independent contributions from each of these sources are combined
tically to quantify the upper error bound and probable error. The probable
s on a root-sum-of-squares (RSS) basis. RSS uncerta ty cal lations also
th cted error distribution.
t uncertainty figures for individual components may be provid
m used to convert between the two units:
= (10 (UdB/10) - 1) × 100
and
U
dB
= 10 × Log
10
(1 + (U
%
/ 100))
6.2.2 continues discussing each of the uncertainty terms in more detail while presenting some of their values.
2.3 provides Power Measurement Uncertainty calculation example for a CW Power sen
nt ets.
Contributions.
ent uncertainty is calculated by combining the following term
Uncertainty Source Distribution Shape K
1. Instrument Uncertainty Normal 0.500
2. Calibrator Level Uncertainty Rectangular 0.577
. Calibrator Mismatch Uncertainty U-shaped 0.707
.577
T
w
3
4. Source Mismatch Uncertainty
U-shaped 0.707
5. Sensor Shaping Error Rectangular 0.577
6. Sensor Temperature Coefficient Rectangular 0.577
7. Sensor Noise Normal 0.500
8. Sensor Zero Drift Rectangular 0
9. Sensor Calibration Factor Uncertainty Normal 0.500
he formula for worst-case measurement uncertainty is:
U
WorstCase
= U
1
+ U
2
+ U
3
+ U
4
+ ... U
N
here U
1
through U
N
represent each of the worst-case uncertainty terms.
Application Notes
6-5