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ADS130E08 3 Phase

Bogdan
Prodigy 80 points
Other Parts Discussed in Thread: ADS130E08, OPA316

Hello,

I need to use the ADS130E08 to measure 3 phase power. Each phase would need to be deferentially measured in reference to ground. Figure 42 shows a diagram of how to wire in a line relative to Neutral. 

Does the voltage divider (R2/(R1+R2)) need to make sure that the voltage across the top R2 is at a maximum of 4 volts?

Does the neutral line also need the same division values of resistors as the power line?

When connecting three phases of power to the same chip, do I need to have a separate set of input resistors (6 resistors) per phase? 

Also, all three phases would connect to the OPAMPOUT pin in parallel with each other, correct?

Thank you for your help in advance!

  • 0
    TI__Mastermind 23235 points

    Figure 42 (from the datasheet) is provided as a simplified reference for how the measurement can be done.  Other implementations can be accomplished for different sensing methods.  This is strictly up to your design.

    Additionally, the above circuit shows the concept of the measurement.  This doesn't completely address safety needs and you should make sure you address protection needs as they pertain to your system and safety specifications.

    The example circuit should the circuity for measuring one channel.  Additional channels/phases will need the same circuitry since the measurement is different.

    If you creating a system that measures 3 phases using the above circuit example, you will probably want to provide an external buffer to provide better drive than the internal op-amp is capable of driving

  • 0 in reply to Greg Hupp
    Prodigy 80 points

    Okay, and is there a reference to any material of what the internal opamp can handle. Or reference to external buffers in relation to the ADC?

    Thanks

  • 0 in reply to Bogdan
    TI__Mastermind 23235 points

    Page 4 of the datasheet shows the drive capability of the internal op-amp.  As long as you still have some headroom to that number, you can use it directly (the datasheet value is a typical).  You can determine the current required based on your input circuitry to the ADC (for all channels you connect the op-amp to).

    If you need an external amplifier, you probably want something with low-offset, low-drift to reduce any errors that you would contribute through the external circuitry. You could take a look at something like the OPA316/7 for a place to start.