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PGA305: Bridge excitation and temperature

Part Number: PGA305

I am looking at using PGA305 for pressure/temperature measurement.

However, I would like to get the temperature by essentially using the bridge resistance as a temperature sensor instead of external temperature sensor.

Can I configure the connections as follows:

Or as follows:

Please let me know if the first or the second option is acceptable or both.

Please also note in the above two circuits the temperature sensor will be replaced by a low Tc resistor.

Thanks in advance!

  • Gents, do you see any images from my question? Do they need approval before they appear in my post?

    Please let me know if I have to re-post the question.

    Cheers

  • Hi Dimo,

    I can't see the images in your post. Can you please edit your post and re-upload them? This may not be the problem you are facing, but in the past I have noticed that the images will not show up if I copy and paste them directly into the reply. You can use the image upload button to make sure they are attached properly.

    Regards,

  • Thank you Scott

    In my first post I pasted the images directly.

    I would like to measure the bridge resistance and use its temperature dependence instead of using an external temperature sensor. 

    This is quite beneficial to my application.

    I looked at PGA305 and I though of two possible ways this can be done. It would be good if you can validate if this is possible and which method would be better.

    Option 1:

    Option 2:

     Would any of these options work. Which one would be better if both work. In Both cases we replace the temperature sensor with a resistor with fairly good temperature behavior, we supply the bridge current from the LDO and we turn off the constant current generator.

     

  • Hello Dimo,

    Both options are effectively the same since the BRG- input is connected directly to ground. It would most likely be simpler to connect to ground externally, but that is really up to you. The main thing to keep in mind with this topology is that the single-ended inputs to the PGAIN amplifier do not go out of spec due to the shunt resistor connected to the temperature inputs. The single-ended voltage at the PGAIN inputs must stay below 1.8V. Make sure that you size your shunt resistor according to the total impedance and span of your pressure sensing bridge.

    Regards,

  • Many thanks Scott, this resolved my question in full