Question, how to measure the accuracy of MMA8451Q ODR Dear team, I would like to ask about ODR accuracy of MMA8451Q. My customer has a doubt on the accuracy of ODR(+-2%) from their test. The customer’s test is as below. Set up the ODR=100Hz by register. Set up the interruption from MMA8451Q when FIFO contains 16 data. MMA8451Q will issue the interruption with 160mS period. As a result, they saw the interruption period from MMA8451Q could exceed from +-2%. Is their test procedure is correct for ODR accuracy measurement? Could you show me how to measure the ODR accuracy? Best Regards, Miyamoto Accelerometers Re: Question, how to measure the accuracy of MMA8451Q ODR Hello Miyamoto-san, Please find below what I got from our product group: The min max 4 sigma value is expected to be +/- 10%. So, 1 sigma is basically 2.5% of ODR. That is the typical deviation. So, ODR +/- 2.5% is the typical ODR deviation (1 sigma). 4 sigma (10%) is the max you could get based on the oscillator. Best regards, Tomas Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka You informed me about the MAX value is related to 4 sigma. So the customer asked me that what sigma value is related to your typical +/-2%. In my understanding, the sigma value is deeply related to the deviation in the viewpoint of statistics. Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello Miyamoto-san, I do not quite understand this question. The percentage should simply be a % of the ODR chosen. 2% of ODR 100 Hz should mean an expected deviation 2 Hz. If this does not answer your question, please let me know. Best regards, Tomas Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka Thanks for your reply! How about the sigma number of the +/-2% typical value? Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello Miyamoto-san, As mentioned before there are no documents about aging accuracy available. Best regards, Tomas Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka > We don’t have any data on aging accuracy but I don’t see it deviating more than +/- 10%. The customer thinks that semi-conductor will not degrade then it will not be deviating more than +/- 10%. Right? If so, do you have any documentations which can back up that? Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka Thanks for your support! Could you show me what sigma values that the +/-2% of the typical value is? Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka Thank for your reply. I will share with the customer. Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello Miyamoto-san, Here is what I received from the product group: The min max 4 sigma value is expected to be +/- 10%. The best way is to measure using a DRDY interrupt as you mentioned. Measure the timing between them. You can also use one of our kits (Sensor board + MCU) and our tools log data with timestamp. That can be the quickest way to get timestamp too. It should be much better than 2% assuming no major temperature extremity. We don’t have any data on aging accuracy but I don’t see it deviating more than +/- 10%. Best regards, Tomas Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka Thanks, I will wait. Please show me the MAX, MIN and aging of ODR accuracy. Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Hello Miyamoto-san, I do apologize for the delay, I am double checking it with the product group and should have an answer by the end of this week. Best regards, Tomas Re: Question, how to measure the accuracy of MMA8451Q ODR Hello TomasVaverka Thanks. > Please note that ±2% is a typical value at 25 °C. From below community thread, I understand that +2% is the Max. Not true? https://community.nxp.com/thread/436100 Please let me know the maximum value. Anyway I will inform the customer the method you gave to me. Regards, Miyamoto Re: Question, how to measure the accuracy of MMA8451Q ODR Dear Miyamoto-san, Please note that ±2% is a typical value at 25 °C. Although customer’s method makes sense, I would recommend a simpler technique without using the FIFO. Just select the ODR, enable the data ready interrupt (INT_EN_DRDY = 1), route it either to INT2 or INT1 (INT_CFG_DRDY = 0 or 1) and then measure changes on the selected INTx pin. . I hope it helps. Best regards, Tomas
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