Is it possible to display a waveform with fixed length and fixed starting point?

[Hao_Liu]

Hi,

I am using DAQ assitant to acquire voltage and current measurment of my device. The voltage is a pure sine wave and current is a periodic waveform with phase difference and distortion. I use waveform chart to display the waveform of voltage and current waveform in seperate charts and they work fine.But the waveforms look like moving to the right all the time, in another way ,the phase is always shifting. Now i want to display the waveforms of both with fixed length (say 2 cycle) and also in a same chart. Apart from that, i also want to display the voltage waveform starting form 0 degree (a fixed point )rather than moving all the time. In this case, i can observe the angle difference between voltage and current. Is there any method to achieve this purpose?

Many Thanks,

Hao

[Norbert_B]

Hao,

first of all, you are using a chart which has three options for updates if the chart is "full":

Strip chart (default)

Scope chart

Sweep chart

These are called "update mode". Test the modes yourself.

Also you have to know that you will not likely have an integer number of periods of your signal in the display of the chart. Therefore, a continuous signal will "move" the graph from update to update.

You can implement some algorithm to discard data to maintain a static "trigger" level for display, but as stated, it will leave gaps in the signal. These gaps are not a concern unless you use the displayed signal for analysis (e.g. FFT).

Norbert