Need I configure ADIS16475 in burst mode

In burst mode need i configure the IMU in the following command  if i want value after bias correction, in other word if IMU take a self-configuration while it turns on.

  • Thank you for your post and for using the ADIS16475 in your work.  Are you asking if the IMU will correct for bias errors at turn on? If that is your question, the answer is no.  You need to wait for the IMU to start-up (data ready starts pulsing), then wait for the internal estimation to settle (32 seconds, for factory default value in NULL_CFG register), then set GLOB_CMD[0] = 1, wait for data pulsing to start again, then set DIN = 0x7E00 to make the first Burst Read request.  Does that help?

  • tks for your reply, i wanna the initialization time IMU which means how much time need i wait for before i collect the value through SPI , if IMU need to wait for 32 seconds  every time it turns on or not.

    and what is the meaning of "set DIN = 0x7E00 to make the first Burst Read request. "?  in datasheet setting DIN = 0x6800 triggers the burst mode

    .

  • We would define "initialization time" separately from managing bias accuracy. Every application is different, in that regard, so that is why we did not make this a mandatory part of the ADIS16475's initialization process. The Allan Variance curve provides you with a tool for evaluating the trade-off between the accuracy of your bias observation and the length of the time record that you use to develop the bias estimates (which will create the correction factors).  Here is what you need to consider:

    • When you execute the bias update, it writes the values to flash, which means that they will automatically load, every time you execute a reset or power cycle.
    • The bias can drift over time (~0.7 deg/sec = Bias Repeatability).  You could approximate this, using a Rate Random Walk (RRW) model of 0.004 deg/sec/sqrt(hour). 
      • Day 1: (24 hours): 0.02 deg/sec
      • Day 2: (from Day 1): 0.014 deg/sec
      • Day 3: (from Day 2): 0.01
      • and so on....the point is, the drift rate slows down over time, when the devices are under stable mechanical conditions.
    • The bias does drift at start-up as well.  Here is a plot of ADIS16465 units, which are similar to the ADIS16475, who were calibrated after a 30 minute warm-up time.  This curve shows you the level of error that you will have, with shorter warm-up periods. 

    Does that help?  I am sorry that this is not as simple as giving you a specific start-up time, but our motivation is to provide you with the most effective options for managing all of the key behaviors in these products.

    I hope that this helps!