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ADS131A02: Rogowski Coil Interfacing for Constant Current Closed Loop Feedback

Karan123
Intellectual 510 points
Part Number: ADS131A02
Other Parts Discussed in Thread: ADS131A04, ADS131E08, ADS131M04, , ADS131A04EVM

Hi,

This is continuation topic of below thread:

https://e2e.ti.com/support/amplifiers/f/14/p/912404/3371493

I have to update PWM Duty Cycle w.r.t for Current measurement from Rogowski Coil to achieve constant current of welding machine(s)  ?

What is the best way for Interfacing Rogowski Coil for Current measurement for High Speed Closed Loop Feedback System ( Not For Energy/Current Measurement after 50Hz or 60Hz) 


I have gone through above part:  Please suggest whether this or another part is suitable for my application. 

--

Karan

  • 0
    TI__Guru* 97795 points

    Karan,


    There are several devices that I think of that may be used for measuring a Rogowski coil. These are the ADS131E08, ADS131A04, and the ADS131M04/M08. These devices are often used to measure Rogowski coils for a particular application. Often they are used for e-meters where the current is measured with Rogowski coil and the voltage is measured with a voltage divider.

    These devices are used for their data rate, resolution, and accuracy. I'm not sure if your application the same requirements as an e-meter, (in particular, I'm not sure what data rate you would require and what latency your application could tolerate).

    Regardless, the devices mentioned previously would be the ones I would start with.


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru* 97795 points

    Karan,

    One other design resource that I'd forgotten to mention is that there is a TI-Design for an e-Meter, using Rogowski coils for the current measurement. Again, it's not your particular application, but there may be more information about the Rogowski coil, and getting the current measurement based on integrating the coil measurement.

    http://www.ti.com/tool/TIDM-3PHMETER-ROGOWSKI

    This design doesn't use a standalone ADC, but it does use a precision delta-sigma ADC integrated into the MSP430. I'm not sure if this would be of help, but I thought I'd mention it.

    Joseph Wu

  • 0 in reply to Joseph Wu
    Intellectual 510 points

    Hi, 

    Sorry for delay in reply .

    Can you Please let me know how much time is needed to acquired (first) result ?

    "The current wave form is reconstructed from the output signal. It is then transformed into an RMS effective value using the following formula:

    Will it possible to take reading in 10ms of 50Hz Sinusoidal Wave form (and Every milli seconds) ?

    with ADS131M04/M08

    Thanks

    --

    Karan

  • 0 in reply to Karan123
    TI__Guru* 97795 points

    Karan,

    For the ADS131A02, there is some latency involved in the readout of the ADC data and when ADC collected the measurement at the inputs. However, it should be able to take readings

    The ADS131A02 has many data rate settings from 1kSPS to 128kSPS (see Table 30 in the datasheet). However, the ADC uses a sinc3 filter, for which the ADC outputs the running average of 3 data conversions. You could consider this ADC latency. In addition to this latency, the ADC data requires an extra conversion period before the ADC data appears on DOUT to be read.

    I explain this with some more details in another E2E post that you can find here:

    https://e2e.ti.com/support/data-converters/f/73/p/913807/3380491


    Joseph Wu

  • 0 in reply to Joseph Wu
    Intellectual 510 points

    Hi,

    Thanks for update and link..

    How to achieve to interface various  Rogowski Coils ?

    Which register need to manipulated ? 

    --

    Karan

  • 0 in reply to Karan123
    TI__Guru* 97795 points

    Karan,


    There isn't a specific interface configuration for Rogowski coils. The ADS131A02 is just an ADC that is measuring a voltage. To program this device, use the initialization sequence shown in Figure 106. Within that flow diagram, you would start communication after receiving the READY word, UNLOCK the device, configure the device (with writing to registers), ENABLE the ADCs, send the WAKEUP command, then LOCK the registers.

    For configuring the device, you would need to program several registers depending on how you want to it set it up. You would set up reference voltage configurations, use of the negative charge pump, data rates, and PGA gains. It's likely you would need to set something in all from registers 0Bh to 14h.

    I recommend that you read the datasheet carefully and review what settings you need to make the measurements. If you are building a system, I would also encourage you to get an ADS131A04EVM to test the measurement of a Rogowski coil.


    Joseph Wu