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INA199: Measuring Current On Single AC Phase

Pete Sampson
Intellectual 480 points

Part Number: INA199
Other Parts Discussed in Thread: TMCS1123

Tool/software:

Looking to add parts to a schematic to measure current draw on a single phase AC line. Considering something like the INA199 with a current transformer based on the App notes I could find but curious if this is still the simplist/suggested method or is there a more complete solution available? Already have an ADC to interface with.

US and Euro wall voltages: 120 and 230V, 60 and 50Hz

Current measured: normally operation is 3.5A, max of 10A

  • 0
    TI__Mastermind 26375 points

    Pete, you need to be careful using these types of products in an AC environment due to common mode limitations. This video will walk you through varying load configurations, but you essentially would have to use one of these devices on the low side where the common mode is kept within these legal ranges to ensure the part is not damaged (you also need to maintain the recommended ratings for datasheet performance)

    For AC applications, we typically recommend our TMCS11xx family of products, such as the TMCS1123. These devices have built in isolation so you would be able to skip the current transformer and measure directly on the line. 

  • 0 in reply to Carolus Andrews
    Intellectual 480 points

    Thanks Carolus, I watched the video and have implemented the TMCS1107A1BQDRQ1 as follows in my design on a 120V/230V line to a VFD/motor:

  • +1 in reply to Pete Sampson
    TI__Mastermind 26375 points

    Pete, 

    No worries! Schematic here looks good. One thing to keep in mind here: our first generation devices do not contain ambient field rejection, so you need to be very careful in how you lay these out to ensure external fields do not couple into your measurement. Check out this app note for more information (specifically section 5) on external fields for the TMCS110x. If this is deemed to be an issue in the design, a higher sensitivity TMCS112x may be a better option here, as it has an inherent 40dB capability to reject outside fields into the part. 

  • 0 in reply to Carolus Andrews
    Intellectual 480 points

    Thanks Carolus, that was super helpful. There will be a lot of magnetic fields around this component so I'm going to switch to the TMCS1126A5AQDVGR.

  • +1 in reply to Pete Sampson
    TI__Mastermind 26375 points

    Pete, 

    Sounds good. Please let us know how else we can help as you move forward in the design.