• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 1 answer
  • Subscribers 32 subscribers
  • Views 2756 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

PGA970: Does PGA970 support 3-wire LVDT sensor

PGA970: 3 wire Setup

Anuj Sharma40
Intellectual 370 points

Part Number: PGA970

Dear Scott,

With regards to a 3 wire probe as per schematic below provided by you, pl let me know if S1N and S2N need to be connected anywhere. Also if they need to be provided internal biasing using VCM_EN and what should be the value.

 

   ,

  • 0
    TI__Mastermind 31655 points
    Hello Anuj,

    I have to confirm some details about the internals of the amplifier section and I will get back to you by 5/8.

    Regards,
  • 0
    Intellectual 370 points
    Dear Scott,
        It would be nice if you provide a complete setup including hardware and firmware settings required for accurate and precise measurements using a 3  wire half bridge LVDT sensor. An application note on same would be highly appreciated later.

    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793

  • 0 in reply to Anuj Sharma40
    TI__Mastermind 31655 points
    Hi Anuj,

    Sorry for the delay. When you select single-ended mode, the amps internally switch to a non-inverting single-ended sense. The gain values remain the same, and the unused input is grounded internally so you will not need to connect anything externally.

    As far as firmware development goes we are currently in the process of adjusting our support model for the PGA970, and this includes discontinuing support of firmware development and algorithm requests on E2E.

    Currently there are software user guides available on the technical documents folder in the PGA970 product page that can be used for reference here: www.ti.com/.../technicaldocuments


    Regards,
  • 0
    Intellectual 370 points
    Dear Scott,
      Thanks for your reply. I have configured the PGA970 in a single ended driver(DAC output mode with P2 tied to VCM/Common mode) and S1 and S2 used in single ended mode(with VCM Bias   disconnected),   to be used along with a half bridge probe from TESA. But I am getting a non-linearity issue towards  the centre of the probe after calibration at two end points. Kindly advise the reason. Also pl let me know the maximum amplitude(peak to peak) that we can extract with a power supply of 5V as  finding it difficult to generate a sine wave more than 1Vpp(with wave spliting. I need atleast 1.5 to 3Vrms. Also kindly explain the working of the DAC values and it's relation to the output sine wave. Kindly take this as urgent as we need to complete the project as soon as possible.

    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793

  • 0
    Intellectual 370 points
    Dear Scott,
       I was wondering if we are sure about the configuration suggested for the half bridge/3 wire  LVDT. Have we tested the same for accuracy/linearity etc. as I am having a very tough time in getting the linearity issue resolved.

    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793

  • 0
    Intellectual 370 points
    Dear Scott,
       Awaiting your response for the issues faced. Kindly do the needful and let me know as we need to finalise design.

    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793

  • 0 in reply to Anuj Sharma40
    Intellectual 370 points
    Dear Scott,

       Awaiting your response for the issues faced. Kindly do the needful and let me know as we need to finalise design.

    Anuj

  • 0 in reply to Anuj Sharma40
    TI__Mastermind 31655 points

    Hello Anuj,

    Regarding the calibration, if your measurement points for the calibration process are only at the end points of the LVDT's travel, the accuracy at the mid point (farthest from the calibration points) will likely be the lowest. Is it possible for you to calibrate a third point as well in the middle?

    The maximum peak to peak amplitude of the waveform generation that you are seeing is about correct. To achieve higher signal amplitudes you will have to implement external amplification.

    In your last question are you referring to the DAC values of the waveform generator?

    Regards,

  • 0
    Intellectual 370 points
    Dear Scott,
       I resolved the linearity issues myself as it turned out to be firmware issues. Yes, the last question i was referring to the DAC values of the waveform generator. As I need an example with actual values on arriving at a sine wave of a particular amplitude, frequency and DC offset. Also, I need to know the purpose and range of the temperature compensation algorithm used.

    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793

  • 0 in reply to Anuj Sharma40
    TI__Mastermind 31655 points

    Hello Anuj,

    The waveform DAC range is 1.25V and it has a 14 bit resolution. The true output on the P1 and P2 pins of the PGA970 will depend on the waveform gain and bias settings that you configure as well as whether you have selected single-ended or differential mode. The PGA970EVM GUI will calculate the DAC waveform codes needed to produce your specified waveform. You just enter the desired amplitude and frequency and configure the biasing and gain and the GUI will populate a waveform table that you can immediately program to the device, or you can save the file for use outside the GUI.

    There is not a premade temperature compensation algorithm available for the PGA970. This will have to be developed by the user for their specific application. E2E support for firmware and algorithm requests on the PGA970 is currently limited to the collateral available on the PGA970 product page on ti.com. You can read more about the current E2E support model for the PGA970 here: http://e2e.ti.com/support/sensors/f/1023/t/802433

    Regards,