Atec Agilent-8990B - Manual (Page 16)

16
Uncertainty calculations for a power measurement (settled, average power)
[Specification values from this document are in bold italic, values calculated on this page are underlined.]
Process:
1. Power level: .............................................................................................................................................. W
2. Frequency: ................................................................................................................................................
3. Calculate meter uncertainty:
Calculate noise contribution
• Noise = Noise-per-sample x noise per sample multiplier
Convert noise contribution to a relative term 1 = Noise/Power ...................................................... %
Instrumentation linearity ...................................................................................................................... %
Drift ........................................................................................................................................................... %
RSS of above three terms ≥ Meter uncertainty = ........................................................................ %
4. Zero uncertainty
(Mode and frequency-dependent) = Zero set/Power = ............................................................. %
5. Sensor calibration uncertainty
(Sensor, frequency, power and temperature-dependent) = ........................................................ %
6. System contribution, coverage factor of 2 ≥ sys
rss
= ........................................................................ %
(RSS three terms from steps 3, 4 and 5)
7. Standard uncertainty of mismatch
Max SWR (frequency-dependent) = .............................................................................................. %
convert to reflection coefficient, | ρ
Sensor
| = (SWR–1)/(SWR+1) = ........................................ %
Max DUT SWR (frequency-dependent) = ...................................................................................... %
convert to reflection coefficient, | ρ
DUT
| = (SWR–1)/(SWR+1) = ........................................... %
8. Combined measurement uncertainty @ k=1
U
C
=
( Max(ρ
DUT
) • Max(ρ
Sensor
) )
2
+
( sys
rss
)
2
.................................................................... %
√2 2
Expanded uncertainty, k = 2, = UC • 2 = ............................................................................................. %
1. The noise-to-power ratio is capped for powers > 100 μW, in these cases use: Noise/100 μW.
Appendix A