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MMR Logging Sampling Frequency at ~98Hz

gjingjin
in General

I've been testing out the newest batches of MMR we got with both logging and streaming mode. (Model # 5, Firmware 1.4.4, Hardware 0.4)

One of the MMR is consistently showing around ~98.4Hz sampling rate for logging mode. Streaming mode appears to be fine. This is done using iOS MetaBase app.

From Eric's post from Sept 2018 I understand that there is a +/-1% error. This appears to be outside the margin of error.

Here is an example:

Calculating Sampling: 3372/34.243=98.47

Suggestions?

Thanks

Comments

  • MattMatt

    @gjin, the data rate is driven by an oscillator internal to the accelerometer and meets +/-1%. There may be a slight additional error or offset introduced when synchronizing the time base of the sensor with that of the smartphone. Is the result repeatable over multiple data captures or longer collection intervals?

    Matt

  • gjingjin
    edited May 2019

    @Matt Thanks for the response.

    Yes, it is repeatable. I have the following tests, all comes out to 98.44-98.45Hz

    ~2min

    ~3min

    ~5min

    ~10min

    ~13min

    This doesn't occur with the other MMRs that I've tested so far from this current batch. We had another MMR from an order last year that also showed this behavior.

  • LauraLaura

    @gjin,
    Must likely the oscillator is not "as good" on this unit as the other MMRs but still within tolerances of the IC manufacturer.

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