PXI

[Denn_Mann]

I would like to know what is the minimum and maximum power output of the CH 0 terminal in my AWG.  It is inserted into a PXI - 1031 dc chassis.  I looked through the attached spec sheet of the PXI - 5422 and on page 10 it lists certain voltage, amplifier configuration, and output power in dBm.  For example, Low Gain --> 1.00 Vpp --> 4.0 dBm seems to be a unit of power conversion because putting the 1.00 Vpp through the power equation gives Pout = 10 * log(V^2/R*1000) = 10 * log([(1.00/(sqrt(2)*2)]^2/50*1000) = 4.0 dBm which is listed on the data sheet .  In my equation,  I have taken the peak-to-peak voltage, divided by 2 to get Amplitude voltage, divided by sqrt(2) to convert to RMS, and then used the power = voltage^2/resistance equation, and finally the Watts to dBm conversion .  I am assuming a 50-Ohm load for this which is what my AWG is currently configured for.

If my analysis is correct, this implies the PXI - 5422 AWG has an output range of -20.5 dB (0.00891 Watts) up to 25.6 dBm (363 mW).  The problem is that the 2 scientists I work with say this is too much power because the output power of the AWG should be able to be directly connected to the digitizer we have (NI PXI-5761) and putting out 25.6dBm will certainly fry it.  According to them, a range of 0 - 10 dBm is more reasonable for the AWG CH0 output power.

Is my analysis correct?  Any additional thoughts?

Thanks for looking!

[Marcus_M · Accepted solution]

Hi,  

This is Marcus from Application Engineering at National Instruments.  I have reviewed over your math and you are correct in your calculations.  To determine the power output of your PXI-5422 you will have to know the Vpp which you are using and also the load that you will be connecting to the device.  These factors will then determine the power output of your PXI-5422. 

Regards,

Marcus 

[Denn_Mann]

Hi Marcus,

It is great hearing from an NI App. Engineer.  I will take my analysis to the scientists to ensure they are up to date on reading the AWG spec. sheet.  Thank you for your feedback.

-Daniel