# How do I know if an AC signal applied to the MDO3000/4000/B RF 50 Ω input is going to exceed the maximum input power rating, and cause clipping, or damage?

### 問題：

How do I know if an AC signal applied to the MDO3000/4000/B RF 50 Ω input is going to exceed the maximum input power rating, and cause clipping, or damage?

### 答案：

MDO3000, MDO4000/B Advanced Math equation will calculate the AC signal's equivalent RF power in dBm, and the automatic High measurement will determine the maximum average power level of the AC signal applied to the 50 Ω analog input channel.

Caution: The MDO3000, MDO4000/B 50 Ω analog input has a maximum input voltage rating of ≤ 5 Vrms

Note: AC signal frequency must be < the maximum analog bandwidth of the Oscilloscope.

AC signal source output impedances that are not 50 Ω will cause impedance mismatches, and will affect signal amplitude, fidelity.

The MDO3000/4000/B setup is very easy.

- Connect the AC signal to input channel 1

- Press the Default Setup front panel button

- Press Autoset front panel button

- Press the input channel menu button and select Impedance 50 Ω

Check the waveform is displayed within the eight vertical divisions (≤ 8V peak to peak)

Adjust the AC signal source amplitude, if needed

- Press Add Measurement, and select source 1 (CH1), measurement type "Cycle RMS"

Check the Cycle RMS measurement is ≤ the maximum 50 Ω input rating, and is not "Clipping"

- Press the Math button and select Advanced Math Edit Expression

- Enter the following equation to calculate power in dBmW:

10xLog(20x(CycleRms(1)xCycleRms(1)))

- Press OK Accept

- Press Display Equation ON

- Press Add Measurement, and select source "M" (Math), measurement type "High".

Check the MDO3000 series Math High measurement value is < +20.

Check the MDO4000/B series Math High measurement value is < +30.

Adjust the AC signal source amplitude, if needed

- Press Ampl front panel button, and select an Ref level > Math High value

- Press Freq / Span front panel button, and select Center Frequency that matches the AC signal frequency

- Press Span button, and select a frequency span one tenth of the center frequency

- Connect the AC signal to the RF input

-Press RF front panel button

Check the automatic reference marker "R" displays the expected frequency and power level.

Note: RF reference marker "R" power level should be similar to the Math power calculation.