PGA305: Calibration coeffients

Igor Giterman

Part Number: PGA305

I am using PGA305EVM-034 for calibrating external bridge.

Format 24bit

Measured 1T3P data is shown in table below:

CALIBRATION TYPE: 1T3P
PRESSURE [psid]	PADC - Decimal Value	Calibrated DAC - Decimal Value
-100	-4790932	1638
0	4750	8160
100	4759893	14685

I computed calibration coefficients and compared with coefficients computed by PGA305 GUI.

Equation: DAC (decimal) = h0 + g0*PADC + n0*PADC^2

My coefficients (show prefect calibration with ZERO error):

h0=8132.309438

g0=0.00136606

n0=1.28E-12

PGA GUI coefficients:

h0=1FEEBD (DECIMAL 2089917)

g0=1661AC (DECIMAL 1466796)

n0=FFFE46 (DECIMAL -442)

TADC GAIN=1

TADC OFFSET=0

PADC GAIN=1

TADC OFFSET=3CA0 (DECIMAL 15520)

I could not find direct correlation to h0, g0 & n0.

Please help with scaling for calibration for coefficients.

Is there a way to attach screenshots?

Thank you for your help

Regards,

Igor

9 months ago

0 Bob Benjamin 9 months ago

TI__Guru** 113765 points

Hi Igor,

Being that you cannot figure out how to attach a screen shot or to add a picture as a file, I have the sense that you may be way over your head trying to get this to work regarding the operation of the PGA305. The PGA is a highly complicated device and requires incredible diligence to get it working. Also, a great deal of research is required to understand the linearization process.

It is not clear to me how you are computing "My coefficients". The EEPROM values in the PGA305 are normalized by 2^22. The generated coefficient values are multiplied by 2^22 before written to the EEPROM. So the coefficient itself must be in the range of +/-1 or less.

I've pointed you to several other E2E posts that outline the process of how this works. I really can't be of any more help beyond this. We have very limited personnel to support these highly complex products. So really the best we can so is to guide customers and then it is up to the customer to figure it out.

https://e2e.ti.com/support/site-support-group/site-support/f/site-support-forum/761619/faq-how-do-i-attach-a-file-or-link-to-my-post/3756691?tisearch=e2e-sitesearch&keymatch=%25252525252525252520user%2525252525252525253A3315#3756691

https://e2e.ti.com/support/site-support-group/site-support/f/site-support-forum/1016585/faq-easy-way-to-insert-screen-snippet-or-image-into-post/3776373?tisearch=e2e-sitesearch&keymatch=%252525252525252520user%25252525252525253A3315#3776373

Best regards,

Bob B

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PGA305: Calibration coeffients