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INA333-HT temperature drifting

Joe Zhou27
Prodigy 40 points
Other Parts Discussed in Thread: INA333-HT

Hi, folks,

I am using INA333-ht for my project, after have spent time to debug, sounds I narrow down the temperature drifting ~15mV by the amplifier itself when around 165C to 175C, do you know if it is supposed to be or something wrong with my design. ~15mV was tested when the input was shorted, pin 5 was connected to a fix voltage.

  • 0
    TI__Expert 4420 points

    Hi Joe, I have a few questions to try to understand your setup a bit better:

    1. What is the fixed voltage connected to pin 5?

    2. The inputs are shorted but connected to what? GND or another voltage?

    3. What is the VDD for the device?

    4. Are the 15 mV the variation you are seeing in the output when you change temperature or how is that measured?

    Thanks,

    JV

  • 0
    Prodigy 40 points
    Hi, JV,
    1. pin 5 is 1.25V
    2. pin 2 & 3 are shorted, connected to a resistor Wheatstone bridge output which has 1K on each leg, the top of the bridge has 2.5V excitation the bottom is connected to ground
    3. VDD is 3.3V, the PCB was placed in a chamber, the temperature reading from the chamber & firmware temp reading were recorded, the chamber is programmed to ramp from 25C to 175C, 3C/min.

    Thanks, Joe
  • 0 in reply to Joe Zhou27
    Prodigy 40 points
    I used a wire connected to pin 6, and monitored the voltage by using 6 1/2 digit multimeter, also the firmware reading was correlated with the actual meter reading for the variations or drifting, it was happening dramatically between 155C to 175C range, negative drifting.

    Thanks a lot, Joe
  • 0 in reply to Joe Zhou27
    TI__Expert 4420 points

    Joe, thanks for the info. I am assuming you have a gain of 1 correct? Is the bridge inside the chamber as well? If so, the bridge resistors will drift as well so we will need to identify whether that is the reason for the INA output to drift. Also, where is the bridge voltage coming from? Could that be drifting as well?

    Thanks,

    JV

  • 0 in reply to Javier Valle
    Prodigy 40 points
    Hi, JV, the bridge is outside of the chamber, the gain: (1 + 100k/300) = 334.3, the bridge voltage comes from 2.5V reference which is about 1.25V as the common mode voltage, I may need to check.

    Thanks a lot, Joe