MSP430FR6989: Not desired when Temprate change.

Hi William,

The LC sensor is sensitive to the ambient environment, like temperature and humidity. You could try to change a low temp draft LC or add the runtime calibration in software. 

HI Gao

 I don't understand what mean runtimecailibration by here. I have a document runtime calibration in document "">www.ti.com/.../TIDM-3LC-METER-CONV". Here, the Code use module AFE2 as an runtime calibration , but it only calib the the drift of amplitude LC signal ( Y axis). when I track the signal LC by temperature , i can see the drift of cycle LC (this T = 2us , f = 500kHz L=470uH, C = 220pF) and drift of internal high frequency (that turning delay of module ESI of Msp430 ) , both is drift X axis. The two drift above , i dont see in runtime calibration document TIDM-3LC-METER-CONV is able to calib.

Could he explain more for me ?

Hi,

runtime calibration can calibrate the threshold of DAC during the working time. The LC drift as you observed the frequency of the LC will change and the delay time is not the point where the max differential value is. If you want to fix this drift you can run the Auto-TSM Calibration to find the new compare point when the temperature is changed. This calibration needs the disc running to finish it.

Hi Gao

Thanks for your answer!. So , I have two more questions.

The first , module ESI of mcu MSP430Fr6989 have two Analog Front End (AFE) , there AFE1 is major and AFE2 is exttra.
The runtime calibration use AFE2 to calibrate the threshold of DAC, but in example code "">www.ti.com/.../TIDM-3LC-METER-CONV" , the AFE2 calibration use result from AFE1 ( signal INTQ6 +1 ) and that means when the disc running continuously , the AFE2 can calibrate the threshold DAC gradually by temperature and module is right. But when the disc is stop in normal condition and suddenly running at any temperature when the drift is too max and AFE1 is worse (no INTQ6 + 1 signal is generated) and it involve the AFE2 cannot run by denpendenting signal from AFE1. That mean in this curriculum , the module doesn't work properly.
I understand as so is right ?

The second , based on answer "If you want to fix this drift you can run the Auto-TSM Calibration ".......

The Auto-TSM() need state of disc is stop , so in case when the disc is running continuously from normal to any point temperature causing error , i can not call function Auto-TSM() to find new drift point , is it right ?

And Do you have any suggestion for me in Water Meter project when use module ESI of MSP430FR6989 when i cannot control environment temperature and when the disc is running or not ?

Best Regards,
William

Hi William,

Got your questions, I can join and try to help you quickly.

Thanks!

Best Regards

Johnson 

Hi Johnson and Allen

Thanks for your feedback, hope you can resolve this question ASAP, our customers is urgent .

Thanks again!

Best Regards,
William

HI all

Any update

Best Regards,
William

Hi,

1. The runtime calibration on the AFE2 is for system only needs a small calibration to follow a small drift. And the runtime calibration also needs to detect four complete rotations to make it work.

In your case, the disk stops and rerorate after a long time. It will need a full calibration including auto TSM and DAC calibration to make it work without errors.

2. Yes. Auto TSM calibration needs the disk stays stop.

3. You should try with some less temperature sensitive conductors.

You can also try to tune you L & C values. frequency=1/2*pi*sqrt(L*C) 

Try to lower the frequency it might help on the temperature drift.

Best regards,

Cash Hao