PGA300: PGA300 External Temperature Sensor

Hello Ed,

Can you please clarify what you mean when you say that connecting with OWI kills the chip? Does it reset the device? Do you need to manually power cycle before it will start responding again?

What do the incorrect temperature readings look like? How are they different from the correct temperature readings?

Regards,

Hello Scott:

Our production calibrated pressure transmitters (with your PGA300 and PT1000 on our PCB), our QC verified 3 points of pressure, and some were out of tolerance, the lab recalibrated them @ 3T3P mode, connected transmitter with 300EVM board, setup OWI, then found internal temperature sensor shows -170C(should be around 20C), and external temperature sensor shows 0.02V at room temperature (should be around 0.39V), all previous calibration coefficients are still there, then re-measure 0-1000 psi, at any pressure it always shows around 378 psi. There is no problem when I use internal sensor for 3T3P calibration.

In previous post months ago, I asked if I need to add 5~10K series resister to PT1000 before ground, TI told me not necessary, today I need to ask again, do I need it?

Thank you for your help! always.

Ed 

If I was using internal temperature sensor, and it did not kill the PGA300 chip when I re-OWI. BUT, if I was using external PT1000, it killed chip instantly when I re-connected OWI. I have tried 5 of them, all killed.

Hello Ed,

I'm still not entirely sure what is meant by the PGA300 getting "killed" is the device being damaged, and it no longer works afterward? Is the compensation engine going into reset? Is the device power cycling and then resuming operation?

You should not need any additional resistance in series with the PT1000.

And to clarify more, it seems like you are able to initiate OWI communication and calibrate the device, but once the coefficients have been programmed and the PGA300 starts running, if you activate OWI again the PGA300 stops working. Is that correct?

Have you tested the temperature sensor with the PGA300 in digital interface mode and seen the expected results?

Regards,

Hello Scott:

I can calibrate it, store coefficients and measure pressure pretty accurate, but I could NOT re-OWI, if I re-OWI it, it would damage PGA300 permanently. If I enter OWI again, 4-20mA always shows 8.35mA, some shows 8.39mA.

Please help!

Ed

Hello Ed,

Do you have any scope captures of the OWI signals before, during, or after the part is damaged as you've said? 

Regards,

Hello Scott:

OWI is always working, BEFORE I re-enter OWI, transmitter works well and accurate, WHEN I re-enter OWI, I can read both internal (-172C) and external temperature (0.02V), because all temperature sensors failed, I cannot re-calibrate it, AFTER I quit PGA300 calibration GUI, the transmitter consistently shows 8.xx mA to any pressure point. I have tried numbers of them, same thing. It seems when I re-enter OWI, the temperature sensor power supply (maybe other power supplies too) was damaged.

I found this issue because few calibrated transmitters among 100+ units were out of tolerance and needed to re-calibrated them, and transmitters with internal temp sensor never had problem, I can re-recalibrate them as many time as I want, BUT transmitter with external sensor was permanently damaged when I first time re-enter OWI.

Please help!

Ed

Hi Ed,

Can you please share your schematic, or at least the parts concerning the VPWR/OWI and the temperature sensor if not the whole thing?

Regards,

Hi Scott:

I cannot publish the schematic here and send it to you thru private message, please check.

Thanks!

Ed

Hi Ed,

Does this issue only occur when the board is used in 4-20mA current output mode? If the output is set for voltage mode, do you see the OWI reactivation permanently damaging the PGA300?

Regards,

Hi Scott:

Because we could not re-calibrate 4-20mA version, we have not started 0-5/10V version yet.

Thanks!

Ed

Hello Scott:

Due to unable to recalibrate PGA300, we only manufacture current output version at this moment.

Thanks.

Ed

Hi Ed,

I need to look at a couple of things in the lab, and I will get back to you by the end of the week.

Regards,

Hi Ed,

Since this discussion was taken offline, I'm going to close the thread for now, and I will come back and update the post when a resolution has been reached.

Regards,