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TDC7201: measuring time between two signals from a photodiode or hallsensor

Pascal K
Prodigy 10 points
Part Number: TDC7201

Hey guys,

I need to find a solution to measure the time between two fast spinning pulleys. I consider to get the signal from a photodiode or a hallsensor. Need to check which one is better.
My smaller pulley is running with round about 1600hz. In combination with the tooth I get 25600Hz for both pulleys. I need to measure a time difference between the  two signals in a range of 5ns. 
Would this be possible with the TDC? And what others components do I need for this.
Is the signal that comes from a photodiode or hallsensor  already suited for the TDC?
Would it be possible to save the data constantly over a longer period of time(minutes)? 

I am a total beginner and dont have really a clue about this stuff.
 

Need more informations? 

Thanks for your help.

Pascal

  • 0
    TI__Mastermind 31655 points

    Hi Pascal,

    Can you provide a little more information about what exactly you are measuring? Is one pulley meant to provide the START signal, while the other provides the STOP signal? Or will you be measuring the rate of revolution individually for each pulley?

    In either case, it seems like the signals coming from the pulleys will be free-running. It is not recommended to apply free-running inputs to the START and STOP pins of the TDC7201, as this could violate some of the timing requirements and result in bad measurements. In order to maintain the proper timing requirements a MUX can be used to ensure that the signals are only seen by the TDC7201 at the correct time.

    Whether additional components are needed between your sensor and the TDC7201 depend on the output of your sensor. Vih and Vil are detailed in the datasheet: http://www.ti.com/lit/ds/symlink/tdc7201.pdf

    The TDC7201 will only store the most recent measurement, or an average of up to 128 measurement cycles. It can be run continuously indefinitely, however you will need to read the results between each measurement cycle.

    Regards,