tone measurement express vi affect the output signal?

[Laurain]

Hi everyone, I am doing a oscilloscope to measure the input signal coming from my analog input of myRIO. I am still new to Labview and I not sure how to implement the tone measurement to measure my signal frequency, amplitude and phase. The first diagram below show the program before i haven't add the tone measurement express vi, the signal get from the waveform graph seem great. However, when i added the tone measurement express vi, the signal seem distorted and unstable. Does anyone know how to solve this problem? Is it the way I implemented is wrong?

 

Figure 1: without tone measurement express vi

Figure 2: with tone measurement express vi