Response time measurements

[Illuminator]

I want to measure the response time of a signal when its frequency is changed from 60Hz to anyother value. I want to create a trigger signal if frequency is changed and then measure the time it takes for the signal to go off. How to create trigger signals based on true/false conditions? Is there a way where i can measure the time it takes the signal to go off when frequency is changed?

Can anyone guide me through this? 

Thanks in advance,

Pavan

[Sarah_Y]

Hi Pavan,

I'm intersted in finding out more about your set up so that I can provide the best answers about how to proceed with your application.  First, what type of hardware are you using?  Different hardware has different capabilities such as counters that will determine what sort of solutions are availible.  Second, are you trying to do this calculation in real time or using digital signal processing after the event occurs? Doing this calculation in real time will be difficult and not accurate.  You will first have to calculate the frequency and then do a comparison of the frequency to your desired number.  This calculation will take several miliseconds and can throw off your measurement.  Finally, is this signal analog or digital?  This will also effect what options you have to make this measurement. 

[Illuminator]

Hi Sarah,

The setup is as follows:  

I am monitoring the Analog AC waveform(60hz signal) using NI 9225 and based on this reference source signal, I have a sine wave analog output . Now, when the frequency of the source signal is changed to 61Hz, the output signal shuts-off.  I need to measure the time it takes the output signal to go to zero after the frequency is changed.

I am trying to do this calculations in real time as i need to see that the output signal shuts off within 160msec(that is the response time of the output signal to input signal variations should be quick).

Can you please guide me through in real time and also how i can go ahead with digital signal processing?

Thanks for your help,

Pavan

[Sarah_Y]

Hi Pavan,

1. What are you using to generate your sine wave?  Bench top arbitrary waveform generator or a function generator?  This will determine if there is a way to create a hardware trigger.

2. How are you calculating when your frequency changes?  

3. How are you measuring that your output signal goes to zero?  Could you please describe what you mean by "go to zero" as well.

What you are using to generate your 60 Hz signal and how you are changing this signal from 61 Hz will greatly determine how much needs to be done in hardware or software.  Regardless, you will need to use your maximum input rate and examine your data to see when the signal changes from 60 Hz to 61 Hz and this change can be correlated to the second channel drop off data.  These two can then be compared to find a delta time in post processing.