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eCAP Module

Hi,
Uses of eCAP Module Reference guid mention:
point1: Period and Duty cycle measurements of pulse train signals
point2: Decoding current or voltage amplitude derived from duty cycle encoded current/voltage sensors

The point1 statement, i implemented in DSP & got the appropriate result with respect to the statement.

Regarding the point2 statement i am not getting properly. So, How voltage amplitude derived from voltage sensor & How SYSCLKOUT synchronise with it?

  • For the purposes of the reference guide, point 2 is really just an extension of Point 1.

    Some types of sensors convert the parameter they are measuring to a duty-cycle or a pulse-width.

    For example, temperature to a PWM output where duty-cycle is proportional to the temperature measured (relative to the ranges that the sensor is capable of measuring).  Another example is IR receiver modules which translate IR signals into pulsewidths. 

    Determining the rate at which a Hall-effect sensor is toggling is another potential eCAP application.


    Thank you,
    Brett

  • -----////////////////----------Some types of sensors convert the parameter they are measuring to a duty-cycle or a pulse-width.--------////////////--------
    which type of sensor converter AC/DC voltage Input to Pulse signal Output?

    As i know that, if Voltage sensor used to measure AC/DC voltage, the output of the voltage sensor is of DC type with a limited amplitude. Am i right, Brett?

    eCAP module input pin requires only Pulse signal to measure width of pulses, then how to measure voltage amplitude i.e not in pulse signal. As eCAP reference guide mentioned that amplitude measurement is possible.

  • Hi Asim,

    There are different ways of solving the problem of sensing analog signals.  One method is coding the amplitude into a duty cycle output.  There are some sensors like this.  For voltage sensing I'd say this is rare when running in the kHz region and I don't have an example for you.

    Note that a delta-sigma modulator/demodulator scheme is similar to this, but at a frequency that will make the utilization of the eCAP challenging.   Some of our newer devices have sigma-delta demodulator peripheral inside our device.

    ===

    You are correct in your statement that the eCAP module cannot measure the amplitude of pulses.  I'll rephrase Point 2 from the document/your first email.
    point2: Deriving current or voltage amplitude from a duty-cycle encoded current/voltage sensor

    If a non-discrete signal needs to be measured, you'll need to utilize the ADC.  If the input signal is periodic, the ADC can be triggered by a PWM event to sample periodically and at intervals. 


    Thank you,
    Brett

  • Hello Brett,

    Kindly give me a appropriate method to solve point2 statement, I'm waiting.
    On be half of my work depend on it (measuring correct voltage amplitude either AC voltage or DC voltage).
  • Hi,

    You haven't provided a good description of what you are trying to do. 

    ==

    In capture mode, the eCAP does not have the ability to measure amplitude.  It is designed to measure the time between the edges of a digital input signal.

    If you need to measure an analog signal, you need to use the ADC.


    Thank you,
    Bret