TIDA-00555: Isolated Current and Voltage Measurement

Adi Selimovic

Part Number: TIDA-00555
Other Parts Discussed in Thread: AMC1100, TIDA-01214, TIDA-00080, TIDA-00738, ADS8588S, TIDA-00834, TIDA-00307, ADS131A04, ADS131E08, TIDA-00661, TIDA-00810, TIDA-00835, MSP430FR5994, TIDA-00929, TMS320F28377S, TIDA-00601, TIDA-01088, TIDA-01094, MSP430F6779, EVM430-F6779

In 3-phase energy applications such as TIDA-00555 and TIDA-00810, is there a possibility to achieve 3 phase isolated measurement by applying DIGITAL isolator after ADC instead of AMC1100 per each channel in front of ADC / MSP? It could be more effective regarding cost and performance (linearity). What are potential obstacles?

Best regards,
Adi

over 6 years ago

0 Jace H over 6 years ago

TI__Guru 56685 points

Hello,

We are trying to find the owner of this TI Design in order to better answer your question.

0 Kallikuppa Sreenivasa over 6 years ago

TI__Guru** 123058 points

Hello Kiev

Digital isolation can provide the required performance and please refer to TIDA-01214 for more details on the digital isolation.

Digital isolation can be applied in cases where you want to isolated the host from the measurement side. This optimizes the cost for sure

If you are using a Current transformer or Rogowski coil, this is possible.

If you are planning to use shunt for current measurement, there is need for channel to channel isolation and you will need to use TIDA-00080 or TIDA-00555.

Could you please provide more details on the application and the volumes ?

Thanks

Sreenivasa

0 Adi Selimovic over 6 years ago in reply to Kallikuppa Sreenivasa

Intellectual 560 points

Hi Kallikuppa,

I am implementing shunt based current measurement due to accuracy requirements. In that case I will use isolation amplifiers (with sigma-delta modulator) interfaced to 16-bit SAR ADC and hope to achieve at least 13 bits accuracy in the end.

Thank you,
Adi

0 Kallikuppa Sreenivasa over 6 years ago in reply to Adi Selimovic

TI__Guru** 123058 points

Hello Adi
looks good. What is the End equipment ?
We have a number of TI designs that you could leverage based on the application
TIDA-00080 and TIDA-00555 which you have already referred.
If you are looking for extended range measurement, TIDA-00738 is a good reference.
For SAR based solution,
we have TIDA-00834 using ADS8588S which is a simultaneous sampling 16-Bit ADC
We have TIDA-01214 and TIDA-00307 for multiplexed 16-bit ADC
We also have Delta-sigma ADCs when high accuracy is required
You could refer to TIDA-00661 with 24-Bit ADS131E08 and TIDA-00810 or TIDA-00835 using ADS131A04 with diagnostics using a 10-Bit SAR ADC.

Thanks
Sreenivasa

0 Adi Selimovic over 6 years ago in reply to Kallikuppa Sreenivasa

Intellectual 560 points

Hi Sreenivasa,

Thank you for huge amount of attached designs. I would interface external ADC to MSP430FR5994 LaunchPad (256 kB FRAM, 8 kB SRAM) - mainly because of data logging possibilities (I want to store huge amount of data) and SCap which provides Standalone mode when it is necessary.

Best regards,
Adi

0 Kallikuppa Sreenivasa over 6 years ago in reply to Adi Selimovic

TI__Guru** 123058 points

Hello Adi
MSP430FR5994 is an excellent choice.
It has a Low Energy Accelerator which can be used to perform spectral analysis (FFT) or digital filtering as required.
In fact we have a TI design TIDA-00929 that you could refer to where we have showcased the device capabilities.
Would you please provide details on the End application and company information?
Thanks
Sreenivasa

0 Adi Selimovic over 6 years ago in reply to Kallikuppa Sreenivasa

Intellectual 560 points

Hi Sreenivasa,

It is 3 phase isolated voltage and current measurement, i.e. power analyzer with logging function. I do it as Student.

Regarding the size of storing values, it will be in a range from 100 to 1000 MB (storing instantaneous values - U and I) and up to 200 kB for calculated values.

My other options were (LaunchPads):
MSP432P401R: 256 kB flash, 64 kB RAM, FPU, 32-bit ARM, 14/bit ADC
TMS320F28377S: 32-bit Delfino MCU, 1MB Flash / 164kB RAM with ECC, 4x 16/12-bit ADC
You are also free to comment my choice.

It has just came on my mind - is it possible to use AMC1304 (which requires additional digital filtering sinc3 by MCU) and MSP430FR5994 without external ADC and thus provide end accuracy for U and I above or equal to 13 bits?

Best regards,
Adi

0 James Evans over 6 years ago in reply to Adi Selimovic

TI__Mastermind 49692 points

Hello Adi,

You may find the following TI Designs featuring isolated shunts helpful as well.

These designs are based on the EVM430-F6779 which uses the MSP430F6779(A) and other devices like the AMC1304.

Regards,

James

MSP Customer Applications

0 Kallikuppa Sreenivasa over 6 years ago in reply to Adi Selimovic

TI__Guru** 123058 points

Hello Adi

It would be good idea to refer to

Multi-phase Energy Measurement with Isolated Shunt Sensors Reference Design (TIDA-00601)

Multi-Phase Power Quality Measurement with Isolated Shunt Sensors Reference Design (TIDA-01088)

Magnetically Immune Transformerless Power for Isolated Shunt Current Measurement Reference Design (TIDA-01094)

and Also

TIDA-00080 and TIDA-00738 in case you want to use AMC1304.

Using MCU or DSP with an internal sinc3 filter module would be recommended.

MSP430FR5994 would need discrete sinc3 filter implementation .

Thanks

Sreenivasa

0 Adi Selimovic over 6 years ago in reply to Kallikuppa Sreenivasa

Intellectual 560 points

Hi Sreenivasa,

Thank you. Sinc3 filter is just provided as a hardware pheripheral?

Best regards,
Adi

0 Kallikuppa Sreenivasa over 6 years ago in reply to Adi Selimovic

TI__Guru** 123058 points

Hello Adi
These are Sigma-Delta Filter Modules internal to DSP or MCU
Thanks
Sreenivasa

0 Adi Selimovic over 6 years ago in reply to Kallikuppa Sreenivasa

Intellectual 560 points

So it is combination of hardware and software if I understood correctly.

Best regards,
Adi

0 Kallikuppa Sreenivasa over 6 years ago in reply to Adi Selimovic

TI__Guru** 123058 points

Hello Adi
Yes that is right.
Thanks
Sreenivasa

0 James Evans over 6 years ago in reply to Kallikuppa Sreenivasa

TI__Mastermind 49692 points

Kallikuppa Sreenivasa said:

Using MCU or DSP with an internal sinc3 filter module would be recommended.

MSP430FR5994 would need discrete sinc3 filter implementation .

Agreed. The MSP430F6779(A) features both hardware modulators and Sinc3 decimation filters in its SD24 module (see block diagram from User's Guide below).

The MSP430FR5994 is also an excellent device with the powerful Low Energy Accelerator (LEA) module that can be used for filtering, but this approach would require more work to implement. Regarding the Sinc3 filter, it does have some inherent roll-off at certain frequencies, and this scenario is discussed in the following blog for your reference.

Quantifying harmonic distortion - Effect of sinc3 filter roll off (part 3)

Regards,

James

MSP Customer Applications

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TIDA-00555: Isolated Current and Voltage Measurement