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ADIS16209 Accuracy Problems and Assembly issues

Question asked by TM31 on Jun 19, 2014
Latest reply on Jul 2, 2014 by NevadaMark
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Hi,

 

we have a program in which there is an ADIS16209 as the mail tilt sensor.

we have tested several units via the evaluation board and they performed to spec.

we had made a PCB design which includes the ADIS16209 on-board (according to app notes and the datasheet rev-c).

in this architecture the ADIS is getting stable and filtered 3.3V from a switched DC/DC converter (ripple is lower than 15mV)

we had made 10 assemblies via automated SMT. from the 10 units only 3 ADIS units were functional!!

we had x-ray tests to see the solder on the pads and the solders were looking good but the units were none functional.

we had opened a new and seals batch of components and made another 7 SMT units built (taking the soldering profile, SMT aliment etc' under great care).

in this batch we had all 7 working but not according to spec or expectations...

we configure the SMPL_PRD to 41 and the AVG_CNT to 8 (the max value) and our testing facility's temperature is 23C-25C:

here are some questions:

  1. in all 10 units were experiencing jitter of about 4-6 LSB in total stable conditions - in the Evaluation units the jitter were about 1-2 LSB
  2. in most units we have a drift in measurements that behaves as if the sensor is measuring a larger angular degree:
    for example: we have a measuring jig which is leveled to 0.1mRad and there we have accurate wedges for 5, 10 and 15 degrees, those wedges are also very accurate. the PCB with the ADIS16209 is placed on a metal bracket with leveled planes which are placed on the testing equipment.
    we see a measurement drift of about 0.05 degree per every angular degree, meaning, for every actual 1 degree our ADIS16209 sensors are measuring 1.05 degree, therefore 5 actual degrees are measured as 5.25, 10 actual degrees are measured as 10.5 and 15 actual degrees are measured as 15.75, etc'
  3. we have larger deviation in the positive side than in the negative side - for example we measure -14.5 and +15.7 at actual 15 degrees
  4. we see that the Y incl axis has significantly higher errors than the X incl axis (the data above represents the Y axis were the X axis shows about 20% less deviation....)

we had gone through all calculations, checked and rechecked the SPI interface and we are currently in a very problematic situation - we have some 100 units which we are not assembling because we don't know why the first 10 are not operating according to expectations....

 

waiting for any help possible!!!

 

Thanks

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