Averaging and Noise Level

Because noise can have a significant effect on the accuracy of RMS

power measurements, settings such as aperture time and averaging are

often employed to mitigate the effects of noise on measurement accuracy.

To improve flexibility, the USB-5680 features two aperture time

settings to offer both high-speed and high-accuracy options. In

“Low-Aperture” mode, the power meter features 15 measurements

per second and in “High-Aperture” mode, the USB-5680 features

1 measurement per second. With these two options, you can choose the

aperture mode and, number of averages to obtain the desired noise level

of measurement. Table 2 shows the number of averages required in both

aperture modes to achieve less than ±0.10 and ±0.01 dB noise levels.

High-Aperture Mode

Low-Aperture Mode

6 GHz True RMS Power Meter with Bus-Powered USB Connectivity

3

BUY ONLINE at ni.com or CALL 800 813 3693 (U.S.)

Ordering Information

NI USB-5680 ..........................................................................780167-01

Includes NI-568x driver featuring soft front panel and API for LabVIEW,

LabWindows/CVI, C, C++, and .NET.

BUY NOW!

For complete product specifications, pricing, and accessory

information, call 800 813 3693 (U.S.) or go to ni.com/rf.

Number of

Averages Needed

for <±0.10 dB Noise

Number of

Averages Needed

for <±0.10 dB Noise

Input Power

(dBm)

Input Power

(mW)

>0

>1.00

1

1

-5

0.32

1

5

-10

0.100

1

1

-15

0.032

1

1

-20

0.0100

1

1

-25

0.0032

1

4

-30

0.00100

1

38

-35

0.00032

4

—

-40

0.000100

39

—

Table 2. Number of Averages, High-Aperture Time Mode

Number of

Averages Needed

for <±0.10 dB Noise

Number of

Averages Needed

for <±0.10 dB Noise

Input Power

(dBm)

Input Power

(mW)

>10

>10.0

1

1

5

3.2

1

2

0

1.0

1

16

-5

0.32

1

78

-10

0.10

1

1

-15

0.032

1

1

-20

0.010

1

7

-25

0.0032

1

61

-30

0.0010

7

—

-35

0.00032

62

—

-40

0.000100

—

—

Table 3. Number of Averages, Low-Aperture Time Mode