why i do get an offset with analog input

[Neo6]

Hello Mr.O,

Regarding the concept I will refer to a communication book. But according to the Labview signal express, if we arre receiving a voltage signal and add a power spectrum step next to the signal acquisition in Signal Express. What is the parameter it is displaying on the y axis which is labled as db rms ref 1.0E+0 V/ sqrt(hz) ? 

My question is how it will calculate power without knowing resistance and current values ????????

[macncheese]

The power will be calculated using the input resistance of your device. If you are using a simmulated signal probably it is using a 1 ohm resistor as a reference.

[Neo6]

In my case I am measuring voltage across resistor of 54 ohms. Sine wave across resistor is given from signal generator. My daq 6361 input impedence is  10 G.ohms.   

Which resistance signal express is considering ??? DAQ input impedence or the resistance across which I am measuring voltage ?????

Thanks and regards

Vaidhin.

[macncheese]

Then you are meassuring the power with the 54 ohm for sure!