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IMU Sensor Selection

Scogg45
on Nov 28, 2012

Analog Devices –

I need help choosing an IMU.

To start, the sensor I am looking at is the ADIS16360.

I will give you a little background on what we will be doing with the sensor. We build and test offshore structures. We have a large wave tank where we generate wave, wind, current and whatever else our clients need. We plan to use this sensor by mounting it inside a structure and record the associated 6 degree of freedom data. It will be dry! The mounting locations will be precisely machined and surveyed in by our model builder. The sensor will ultimately be hooked up to our National Instrument chassis which is our data acquisition system.

The way a normal testing would go is as follows:

Power up system and verify everything is OK. Then we take what we call a “calm” test in still water. Depending on the sensors a model may have this “calm” test serves as a “zero.” Immediately after a calm test, a real test is run. This may include waves, wind, etc. Test duration is anywhere from 20-30 minutes. After that the water calms down for about 30 minutes. Then we do the whole calm test – real test cycle again.

Questions:

  1. Based on my description do you see any issues?
  2. We would like to sample the output somewhere between 100 samples/sec to 1000 samples/sec on each channel. Data will be taken via a national instruments data acquisition system. Is this too high? Would we be severely oversampling? (somewhere I saw 819 samples/sec then I read bandwidth of 16hz)
  3. What are your questions/recommendations?  Please provide part numbers for any recommended accessory that may help in the installation/operation.
  4. Is there a better choice?

I appreciate any help you are willing to give. We just purchased a new National Instruments chassis system and are just now getting to play with all of the cool new digital toys. Sorry for the noob questions.

Thank You,

Jared Scoggins

Texas A&M University

Offshore Technology Research Center

Jscoggins@otrc.tamu.edu

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  • 0
    •  Analog Employees 
    on Nov 29, 2012 1:20 AM

    Hello Jared,

    We have a wide range of IMUs that provide  a trade-space of performance, size, power and cost. The ADIS16360 is on the lowest cost/performance corner of the trade space, but it is hard for me to know what type of motion you expect to track during your waves.  The ADIS16485 provides an upper-end option with roughly 6-8x better noise performance, when compared to the ADIS16360.

    For your ADIS16360-specific questions, the natural sample rate is 819.2 SPS. The 16Hz bandwidth probably came from the filtering section of the datasheet, as an example setting. Here are some suggestions:

    1. The ADIS16360 has a flex connector that can easily be broken when it is not cared for.  You might want to consider an option that has the connector embedded, just to prevent the accidental flex breaks. We offer no repair or warranty for this. The ADIS16334, ADIS16445 or ADIS16448 are options I would consider. I would probably lean towards the ADIS16445 but you will want to make sure that the +/-5g acceleration range will suffice.

    2. For data collection, I would suggest using the nominal sample rate (819.2 for the ADIS16360) and use the data-ready pin to synchronize your reads through the NI system.  The 16Hz reference most likely came from a sentence that offered the resulting bandwidth, when using a specific SENS_AVG (filter) setting.  Correct?

    3. Follow "best practice" approaches to your setup.  Examples of this are: keep your communication cables as short as possible, no hot-plugging, make sure your supply is stable and reliable, check your SPI signals for proper timing/signal integrity/coding. The devices work very well when they are presented with proper power and appropriate SPI signals. Your implementation has an impact on these items. 

    I hope that helps!

    NevadaMark

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  • 0
    •  Analog Employees 
    on Nov 29, 2012 1:20 AM

    Hello Jared,

    We have a wide range of IMUs that provide  a trade-space of performance, size, power and cost. The ADIS16360 is on the lowest cost/performance corner of the trade space, but it is hard for me to know what type of motion you expect to track during your waves.  The ADIS16485 provides an upper-end option with roughly 6-8x better noise performance, when compared to the ADIS16360.

    For your ADIS16360-specific questions, the natural sample rate is 819.2 SPS. The 16Hz bandwidth probably came from the filtering section of the datasheet, as an example setting. Here are some suggestions:

    1. The ADIS16360 has a flex connector that can easily be broken when it is not cared for.  You might want to consider an option that has the connector embedded, just to prevent the accidental flex breaks. We offer no repair or warranty for this. The ADIS16334, ADIS16445 or ADIS16448 are options I would consider. I would probably lean towards the ADIS16445 but you will want to make sure that the +/-5g acceleration range will suffice.

    2. For data collection, I would suggest using the nominal sample rate (819.2 for the ADIS16360) and use the data-ready pin to synchronize your reads through the NI system.  The 16Hz reference most likely came from a sentence that offered the resulting bandwidth, when using a specific SENS_AVG (filter) setting.  Correct?

    3. Follow "best practice" approaches to your setup.  Examples of this are: keep your communication cables as short as possible, no hot-plugging, make sure your supply is stable and reliable, check your SPI signals for proper timing/signal integrity/coding. The devices work very well when they are presented with proper power and appropriate SPI signals. Your implementation has an impact on these items. 

    I hope that helps!

    NevadaMark

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