i want to measure the time interval between two zero crossing instsnts.give me the suggestions

[voltage measurement]

Hi, I am doing the project on position detection.Regarding that i have to solve two problems using labview software.

1) I  have to find the time interval between two zero crossing instants.

2) Is it possible to generate pulse whenever my output crosses zero

 give me suggestions regarding above .

[Jochen]

Could you please provide some more specific information?

What hardware are you using?

What type of output are you using and how do you measure position (sensor type, measurement method)?

What are your input and output operation modes?

What about your timing requirements (e. g. maximum delay between zero crossing and pulse generation)?

What is your LabVIEW version and which operating system are you using?

Thanks, and kind regards,

Jochen Klier

National Instruments

[voltage measurement]

Thanks for your reply sir,

We had a plan to measure the voltage of motor using any DAQ available in our Lab.That is our future plan.

 Before that  we are trying to  create such voltage using labview software alone.

 That motor back emf(voltage ) is normally trapizoidal one.

The position information is going to find without any sensors but from the waveform zerocrossing instants.

The zero crossing instants of this trapizoidal wave will directly give the switching instants for our inverter control.

hence please give suggestions to create the trapizoidal waveform and also pointe out which is the easiest method to find the zcd.

we have to generate the pulses at every zero crossing instant and also we have to calculate the time interval between two consequent zero crossing instants .will this all possible using labview software?.

we have labview8.5 in our lab.

Expecting your reply

thankyou

[Jochen]

So let me step back a bit to see if I understand you correctly. For your application it's ok to control the motor's velocity in open loop control by outputting an analog waveform. You need to send a digital pulse that is synchronized to the zero crossing of this waveform.

Such a task can be accomplished with a simple DAQ board like the PCI-6221. This board supports correlated digital I/O operations, so you can output an analog and a digital waveform simutaneously synchronized to the same update clock. As you define the analog output waveform, you should know the zero crossing point. E. g. if the zero crossing occurrs after 1000 updates of the DAC, you could define a digital waveform that contains 999 LOW followed by 1HIGH value.

As you know the waveform and as you can determine the board's timing, the time interval between zero crossing is a known value.

I hope this helps,

Jochen