:SOURce:POWer[:LEVel][:IMMediate][:AMPLitude]

Description

Gets or sets the sources power level in dBm. The relation between source power level and source voltage can be described as follows.

Figure: Signal Source

Referring to the figure Signal Source above \(V_0\) describes the internal source voltage and \(V_\mathrm{S}\) the voltage at the output connector which depends on the load (e.g. half of \(V_0\) at \(50\Omega\) load). The output power level \(P\) in \(mW\) is always calculated for a \(50\Omega\) system. Therefore the chosen output power level \(P\) defines the internal source voltage \(V_0\).

\[ V_0 = 2\cdot\sqrt{P\cdot 50\Omega} \]

The output power \(P\) in \(mW\) and the output level \(L\) in \(dBm\) can be converted into each other.

\[ P = 10^{\dfrac{L(dBm)}{10}}mW \]
\[ L(dBm) = 10\cdot\log_{10}\left(\frac{P}{1mW} \right)dBm \]

Typical use cases for loads include high impedance (high \(Z\)) and a \(50\Omega\) load. For a desired output rms voltage \(V_{\mathrm{S}}\) the necessary setting for output power level \(L\) in \(dBm\) can be calculated for these cases.

\[ \text{$50\Omega$ load:} \quad L(dBm) = 10\cdot\log_{10}\left(\frac{V_{\mathrm{S}}^2}{1mW \cdot 50\Omega} \right),\quad V_0 = 2 \cdot V_{\mathrm{S}}\\ \]
\[ \text{High impedance $Z$:} \quad L(dBm) = 10\cdot\log_{10}\left(\frac{V_{\mathrm{S}}^2}{4 \cdot 1mW \cdot 50\Omega} \right), \quad V_0 = V_{\mathrm{S}} \]

Syntax

:SOURce<ch>:POWer[:LEVel][:IMMediate][:AMPLitude]

Command Query
Query Response
Yes Yes The sources output level in dBm.
Parameters
Accepted Format
Allowed Suffixes
Possible Errors
Description
{ <numeric> | MINimum | MAXimum } Range from Min. power to Max. power none none The sources output level in dBm

To learn more about channels and traces, please refer to the SCPI command structure

Sample usage

Set the sources output level to 10 dBm.

visaSession.write(':CALC:PAR:DEF GainPhase\n')
visaSession.write(':SOUR:POW 10\n')

:SOURce:POWer
:SOURce:POWer:MODE
:SOURce:POWer:LIST:FREQuency:POINts
:SOURce:POWer:LIST:FREQuency
:SOURce:POWer:LIST:AMPLitude:POINts
:SOURce:POWer:LIST:AMPLitude