Urgent Help needed!!! probably some really good expertise

[apekshit]

Hi ,

I am sending you the VI on which I am working.I am basicalaly measuring the capacitace , Voltage and Conductance using this VI. But all I WANT IS HOW FREQUENTLY IS CAPACITACNE MEASURED.

If you look at the stacked sequence structure, In sequence No. 2, we measure the capacitance value and conductance value as primary and secondary values respectively.

Now my question is if one value of capacitance is displayed when is the next value displayed , I mean is it a way to calcuate the time difference between measurement of capacitance  using the VI HP428XA Set bias function. I want to measure the time difference between measrement of each capacitance value by the system.Just wanted to know how does does my system measure the value of capacitacne.

Any help is appreciated.

[Dennis_Knutson]

It's not clear to me what time difference you want to measure. Is it the time between one sequence and the next, the time it takes one frame to exeucte, or is the time between iterations of the loop? In one of your earlier posts, you were given an example on how to get the start time in one frame and then in another frame, determine the time spent in a previous frame. To determine time between iterations, you can get the current time, store it in a shift register, and then the next iteration, subtract the new current time from the value in the shift register.

[apekshit]

Well, Basically what I need is as follows. Sequence 2 (0..3) in the stacked sequence structure has a VI that outputs the value of capacitance for display.. now we are using this Labview program to measure the Capacitance -Voltage characteristics of a MEMS device. Now the changes in capacitance are very facst and in the range of 10^-15 farads. Hence, My intention is to measwure how fast the value of capacitance changes when it is given to the display of Capacitance(pF).Note that here the capacitance is measured in pico farads.

So, Please suggest if possibel make changes in the VI and send the VI which will allow me to measure the time difference (In m,ico seconds) that shall be elapsed when one value of capacitance is displayed and the next value of capacitance is displayed.

The frequency of change in capacitance value that can be measured by the Labview program for LCR Meter needs to be measured.

[Dennis_Knutson]

The VI you have in frame 2 is not in the driver so I can't tell what's in it, but assuming that you have a 0 second delay in frame 1, you're going to have a very difficult time measuring elapsed time  in microseconds. The clock in a pc is only accurate to a couple of milliseconds and I'm not sure how fast the instrument can be programmed for a new bias voltage and then read again. You could put a Get Date/Time in Seconds in frame 0 and another in fram 2 and then subtract the two but I wouldn't want to depend too much on the result.