User`s guide

Specifications and Characteristics 11
N1911A/1912A P-Series Power Meters User’s Guide 269
Noise and Drift
11
Within 1 hour after a zero, at a constant temperature, after 24 hour warm-up of the power meter.
This component can be disregarded with Auto-zero mode set to ON.
12
Measured over a one-minute interval, at a constant temperature, two standard deviations, with
averaging set to 1.
Effect of Video Bandwidth Setting:
The noise per sample is reduced by applying the meter video bandwidth filter setting (High,
Medium or Low). If averaging is implemented, this will dominate any effect of changing the
video bandwidth.
Sensor
Model
Zeroing Zero Set Zero
Drift
11
Noise per
Sample
Measurement
Noise
(Free Run)
12
<500 MHz > 500 MHz
N1921A /
N1922A
No RF at
input
200 nW 100 nW 2 µW 50 nW
RF Present 550 nW 200 nW
Measurement
Average Setting
1 2 4 8 16 32 64 128 256 512 1024
Free Run Noise
Multiplier
1 0.9 0.8 0.7 0.6 0.5 0.45 0.4 0.3 0.25 0.2
Video BW setting Low
5 MHz
Medium
15 MHz
High
30 MHz
Off
Noise per Sample
Multiplier
<
500 MHz
0.5 1 2 1
≥ 500 MHz
0.45 0.75 1.1 1