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MSP430I2041: i2041 How to increase accuracy.

Part Number: MSP430I2041
Other Parts Discussed in Thread: TIDM-SERVER-PWR-MON

Hi MSP Team,

My customer designed a single phase meter based on MSP430i2041 using TIDM-SERVER-PWR-MON as reference.

This meter has some problems. 

When the USB is connected with PC for debugging, the circuit breaker goes down.

I guess the cause is that the AC and DC grounds are not separated.

Could you review schematic? If it is possible, I would like to send the schematic by personal mail.

The other problem is the measured value is not correct. 

1. The current is high  and active power is negative when there is no load.

Voltage in mV: 228012

Current in uA: 217837

Active power in mW: -44064

Reactive power in mW: 22945

Apparent power in mW: 49669

Power factor in 0.001 in mW: 8871

Frequency in 0.01 Hz: 6069

Voltage channel DC offset: 14502

Current channel DC offset: -1249715

2. When he removes two beads FB3, FB4, measured current is not zero.

Is it correct that the current will be zero when the beads are removed?

He made 20 boards and most of them have this problem.

How can I increase accuracy?

  • I think you can refer to the EVM-F6736. Please pay attention to the power setting, it connect one power line directly to DGND and AGND. Please check the power

     setting first, it use a half bridge not a full bridge. The reason is that you need to make sure the input voltage for SD-ADC is what you exactly want.

    You can also use isolation between AC and DC (few customer use this solution because of cost), but remember to connect one line to DGND as well.

  • Hi,

    Why are the current and the active power high in the no load mode?

    He read abnormal values from many boards.

    [Abnormal Value]

    Voltage in mV: 228012

    Current in uA: 217837

    Active power in mW: -44064

    Reactive power in mW: 22945

    Apparent power in mW: 49669

    Power factor in 0.001 in mW: 8871

    Frequency in 0.01 Hz: 6069

    Voltage channel DC offset: 14502

    Current channel DC offset: -1249715

    [Normal Value]

    Voltage in mV: 227727

    Current in uA: 41849

    Active power in mW: 988

    Reactive power in mW: -9156

    Apparent power in mW: 9530

    Power factor in 0.001 in mW: -1036

    Frequency in 0.01 Hz: 6063

    Voltage channel DC offset: 4222

    Current channel DC offset: 843991489

  • Can you check the input signal of current channel? This can helps know if the root cause lies on hardware or software.

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