I have some question about calibration process and program(sboc320c PGA309EVM UsbSoftware download from TI site).
For two weeks, I tested using PGA309EVM-USB kit and sboc320c PGA309 Usbsoftware to find temperature calibration method.
So I have many question to be advised from you.
The condition is below.
Test condition
- PGA309EVM-USB Setting
External Pressure sensor 0~ 100psi absolute
Temperature sensor – Internal sensor of PGA309
Communication – 4-wire connection
Vref – internal (4.096V) , PGA309 REFIN/REFOUT PIN- disconnected
Vs=Vsa=Vsd=5V
PC – Window XP
Calibration program : sboc320c PGA309EVM UsbSoftware
Range
Pressure : 4 psi ~ 96psi
Voltage : 0.2V ~ 4.8V
Operating temperature : -10℃ ~ +10℃
Calibration
Temperature point and order : 3point, -10℃ -> 0℃ ->10℃ ( -10℃ is the first calibration temperature)
Pressure-Vout Max/Min : 96 psi-4.8V / 4psi-0.2V
In the temperature chamber.
Q1. When I bought the kit(PGA309EVM-USB), there was CD containing software sboc320 not sboc320c.
What is the deference between two version? I think they have much difference,
especially the number of calibration temperature and saving data to external EEPROM.
Q2. After calibration at -10℃, I raised temperature to 0℃. During that time, I powered the kit on.
Can I turn off the kit during that raising time, which is not related to calibration?
If not, the kit should be powered on during all the calibration process including temperature raising time. Right?
Q3. At the ‘1. Configure internal temperature’ and ‘2. Configure calibration’ in ‘question.pdf’, the settings are
correct for the test condition above?
Q4. In the added file ‘question.pdf’, I set to use internal temperature sensor with reference voltage of internal 4.096V.
The calibration result is picture ‘4.Calibration result’. After downloading this result to EEPROM, I read back external
EEPROM. The read data is added as text file and can be seen using PGA309EVM UsbSoftware
If you compare this with ‘4.Calibration result’ in the added file, you can find abnormality.
Referring to the usual manual(sbou024B, page64), the data in the red box(⑤) in the ‘4. Calibration result’ should be in T0, T1, T2 of EEPROM in order
That are T0 -> FF64 , T1 -> FFE4, T2 -> 85
But EEPROM data was not. Is this software bug, or correct?
Q5. In red box ② of ‘1. Configure Internal temperature sensor’ in ‘question.pdf’, should I use both option
simultaneously ? That are ‘Continuous Conversion’ and ‘Single Shot Conversion’.
Q6. In the ‘Internal Temperature Sensor.pdf’, I tested two cases for internal temperature sensor reference voltage.
One is to use ‘Temp ADC internal Vref(2.048V), the other is to use internal Vref(4.096V) as reference voltage.
The result pictures of reading PGA309 are included . A temperature is 25℃,
I think the second method is correct reading, but the first is not. Is this also bug of this software(sboc320c)?
Q7. The Look Up Table (The second part, from address 16 to 119) of external EEPROM.
If the number of calibration temperature is 3, after calibration process, how does the calibration data stored
in the EEPROM? When I test this using sboc320c PGA309EVM software the data stored from T0,Z0,G0
to T16,ZM16,GM16 with values which I cannot understand. How does this work?
Q8. Should the interval of calibration temperature point be same? I mean if I want to use PGA309 in the temperature
Range from -40℃ to 100℃ and calibrate at five temperature point, should I calibrate at temperature
-40℃, -12℃, +16℃, +44℃, +72℃, +100℃ with same interval 28℃.
I hope you can advise me.
Thank you.
Hello Seok-Bong Yoon,
Thank you for your question regarding the PGA309. I have deleted your other post (which only had these uploaded files) and moved them to this thread.
My computer is being repaired today, and Monday is a holiday here in the U.S., so I will unfortunately not be able to completely answer your question until Tuesday. On Tuesday I will attempt to duplicate some of the bugs you are observing in the software and confirm the proper settings for your application. I apologize for the delay.
3036.0882.Internal Temperature Sensor.pdf
7345.5557.question.pdf
Best regards,
Ian WilliamsLinear Applications EngineerHigh Performance Linear and Sensing Products
Dear Ian.
When can I have your reply for my question?
If you don't understand my question, please let me know.
Sincerely yours.
YOON
Hi Yoon,
I will answer your question within the next few days.
Ian Williams
A1. There are significant improvements and bug fixes in the new version of the software, Rev. C. You must use the most current version of the software.
A2. You can not turn off the EVM during calibration. The calibrated values are not written into the EEPROM until the very end of calibration. If you power down the hardware before calibration is complete you will not get accurate performance from the device.
A3. Your settings for "Config Temp ADC" are correct.
I have a question about your "Create Pre Cal File" settings. What is used to excite the pressure source? Does it not require an excitation voltage? Typically this is what Vexc is used for, so it's usually enabled. Also, I recommend checking "Calibrate Nonlinearity (LinDAC)" for best accuracy.
A4. The readings in the "Temp DAC" column are correct. However, you did not upload the EEPROM data text file so I cannot compare those readings.
A5. You can check both boxes (Single-Shot and Continuous Conversion). It is a common configuration and will not cause problems.
A6. This is not a bug in the software. The Internal Temp ADC reference should not be enabled when in Internal mode. I realize that this is slightly confusing, but the settings are confirmed by the PGA309 User's Guide. If you go to p. 113, section 6.2.7, you will see that when bit TEN=1 (enable internal temperature mode), you must set bit AREN=0 (disable Temp ADC internal reference).
A7. The software always creates a set of 17 temperature coefficients (T0, Z0, G0 to T16, ZM16, GM16) to write to the EEPROM after calibration. These coefficients are used for temperature correction at all temperatures inside your temperature range. All 17 coefficients are written, even if you only have 3 temperature measurement points.
A8. It is not required to calibrate at the same temperature interval. For example, if your range was from -40C to 100C, you could calibrate at -40C, -10C, 25C, 60C, and 100C. The calibration software has logic that can determine the right set of temperature coefficients, regardless of which temperatures you use to calibrate. However, you must always calibrate to the minimum and maximum temperatures.