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PGA300: Fever problem

Cera Wei
Intellectual 2010 points
Part Number: PGA300

Hi team,

My customer now uses PGA300 for pressure transmitter, but met fever problem when the power supply is 20V and the output current is 20mA. The inside temperature sensor can't be used for temperature calibrate.

Power supply

Output current

Last time

TADC

Temperature

20V

2mA

5min

1CE3

27.6

20V

20mA

5min

1DBA

35.9

So they tried to use the external sensor, but the pressure sensor is excited by current,  the connection is as follows, there's no input port for the temperature sensor.

So do you have any idea for the following questions:

1. How to use an external temperature sensor when the pressure sensor is current excitation?

2. How to calculate  thermal loss? And in what condition can we use the internal temperature sensor (the biggest voltage and current)? 

Thank you!

Best regards,

Cera

  • 0
    TI__Mastermind 31655 points
    Hi Cera,

    Part of the problem with the current setup is that the bottom of the sensor bridge should be connected to the device ground, and not to the INT- pin. This can be used, but it is dependent on the amount of current desired, and the impedance of the bridge. If the bridge impedance is too high, the internal current source can run out of headroom, and will not output the correct current. Do you know the total impedance of the bridge, and what current setting the customer is using?

    1. You can not use an external temperature sensor while also using the internal current source to excite the pressure sensor.

    2. Could you please explain this question? Are you asking for how to compensate for temperature with the calibration?

    Regards,
    Scott Cummins
  • 0 in reply to Scott Cummins
    TI__Mastermind 31655 points
    Hi Cera,

    Do you have any clarification for the second question?

    Regards,
  • 0 in reply to Scott Cummins
    TI__Intellectual 2010 points
    Hi Scott,

    Sorry for late.

    1. The impedance of the bridge is about 10k, and the current is 250uA;

    2. The second question is that I want to analysis the thermal of PGA300 and the external triode (for 4-20mA), because I doubt the fever may result from the triode.

    Great appreciate your kindly help！

    Best regards,
    Cera