Regarding Voltage Reference level for PWM signals(Duty cycle measurememt)

[Nithu]

If anyone have solution for this below problem please provide me ASAP.

We have used “Timing and Transition Measurements” and configured for the measuring of Duty cycle. We have used PXI 6115 and digitizer and programmed to measure the duty cycle by applying 500Hz signal with 50% and 80% ranges .We observed the wave form through the oscilloscope and found that edge are curved and not has sharp edges. The Voltage range we used is around 14V and we attached the Snapshots with the wave form contains the curved edges.

Below is the help and calculation available in the “Timing and Transition Measurements” for deriving Duty cycle

Pulse duration—Calculates the time difference in seconds between the first two middle references level crossings. Pulse duration also is known as pulse width.

Period—Calculates the time in seconds between adjacent middle reference level crossings in the same direction. The reciprocal of this value is the signal frequency.

Duty cycle—Calculates the Pulse duration as a fraction of the Period.

Please clarify the following points.

1. Can u please provide us the information that how to configure for measuring the duty cycle by changing the reference levels (voltage level)?

This will help us to configure the voltage level to handle our exception for curve edges with high frequency in our application. 

2. Is that the “Timing and Transition Measurements” will automatically take the reference levels and calculate the duty cycle. Is it right?

Thanks & Regards

[mallorim]

Hi Anitha,

Are you using the Timing and Transition Express VI? This express VI, because the code is written for you, can be relatively limited in the provided functionality. I do not believe that there is a way to set the reference levels. If you are interested in doing so, I would look at the example program entitled Pulse and Transition Measurements. This example VI generates a signal set up by the user in the first case structure and then analyzes the signal for a number of settings in the middle case structure. On the block diagram, if you look at the Pulse Meas. case of the middle case structure, you will see it contains the Pulse Measurements.vi, which outputs period, pulse duration, and duty cycle based on the inputs of the signal and a cluster of numeric reference level controls. This function will, I believe, give you the fine control you need.

Hope this helps,

Mallori M.