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Questions about TIPD205(TI Design) applying DRV425

hideyuki sakai
Mastermind 6250 points
Other Parts Discussed in Thread: DRV425, TIPD205

Dear, Sir.

My customer is considering to measure DC+/- 400 ~ 600A.
It looks possible to refer TIPD205 appying DRV425.

Could you please tech us several things because we are not familiar with the product.

1. DRV425 Fluxgate.
 a) I have a chance to see the principle of Fluxgatre, before.
   It was configured with Excitation, Sensing, Compensation coils & 2 magnetic core
   (Non-Inveting, Inverting).
   I wonder DRV425 is integrated the Exciation portion inside the ic?

2. TIPD205.
 It is mounted 2 pcs of DRV425 to measure the absolute position, and show as Voffset. 
 b) I wonder the influence of geomagnetic & adjacent fiild will be observed on Voffset?
 c) I wonder DRV425 is just measured above, So won(t do automatic correction, it will be
     implemented by external MCU to capture the signal through ADC?
 d) Is it possible to realize +/- 100A DC current sense using just 1 DRV425?
     If yes, Please let us know the bottle-neck to realize that(for instance, accuracy got
     worse than the case of 2 pcs DRV425 because the current unbalance on rght/left side
     of hole could not be involved, etc)

Best Regards,
H. Sakai

  • 0
    TI__Mastermind 18780 points
    Dear Hideyuki,

    I've asked Javier to have a look at this. He should hopefully respond soon.

    Thanks!

    Carolus
  • 0
    TI__Mastermind 26475 points

    Dear Hideyuki,

    Question 1)

    Yes the DRV425 has everything integrated including the excitation inside the IC.

    Question 2)

    There is two way the near fields will be observed.  One is there will be a change in the VCM output voltage.  Also there could be an error in the Vdiff voltage depending on the proximity of the source and the strength.  There are a few way to help reduce the error by reducing the hole size, changing orientation and changing sensor separation (distance between DRV425).  One signal can be obtain by each DRV425 but the bus bar application uses the properties of the gradient fields in the hole to it's advantage and any small errors in placement will not have a high impact on the measurement.

    Regards,

    Javier Contreras

  • 0 in reply to Javier Contreras4
    Mastermind 6250 points

    Dear, Javier-san. 

    Thank you so much for your teachings. 

    My understanding is getting clear little bit due to that. 

    Below are my understandings, Please correct if there were miss-understanding. 

    1. TIPD205 has 2 DRV425's. Major error can be cancel to take voltage difference

        between Vout(Vdiff) & Vcm, because the one signal detected 2 DRV425 so the

        error observed same voltage direction on each output. 

    2. There are much of difficulties on just using 1 DRV425 hoiw to cancel above 

        major error. 

    3. On DRV425 datasheet, we can see the definition like, min -8, typ +/-2, max +8. 

        It is meaning typ is under room temp & min, max are under -40 or +125 deg.C. 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Mastermind 26475 points

    Dear Hideyuki-san,

    1)  The difference is already taken care of with the analog circuit.  Vout(Vdiff) is measured with respect to Vref and this voltage already calculates the difference between both DRV425.  (I will attach a document on a later day with more description on how it works.)

    2) One DRV can be used but location is more critical and knowing that distances as well.  Also the common fields and neighboring fields can cause errors that are not as easy to calibrate out.  I would recommend against this.

    3)  Room specification is +/- 8uT offset with a typical of +/-2uT.  The drift from room is 5nT/°C.  So worst case should be 8uT + 100°C(5nT) = +/-8.5uT.

    Regards,

    Javier

  • 0 in reply to Javier Contreras4
    Mastermind 6250 points

    Dear, Javier-san. 

    I am feeling a mount of gratitude for all of your valuable teachings. 

    My private E-mail is; 

    hideyuki_sakai@marubun.co.jp

    Please use if it was better for you. 

    Best Regards, 

    H. Sakai