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Original question:

Magnetic sensor

How to measure electro-magnetic field?

Xiaoxuan Lu
Prodigy 130 points
Other Parts Discussed in Thread: DRV5055, DRV5057, DRV5053, DRV425

Hi,

I am wondering out of many magnetic sensors of TI, is there any one can measure the AC values of the (electro-)magnetic filed generated by powerlines? 

I know most TI Hall effect sensors are designed to measure the DC component, but I am wondering whether a time-varing  AC component can be measured here. 

  • 0
    TI__Mastermind 26395 points

    Hello, 

    Thank you for using the TI forum.  The magnetic field from an AC component can be measured with our bipolar linear sensors, as long as the sensor sampling frequency is fast enough compared to the AC frequency. Here are a few options for you to consider:

    1) DRV5055: High accuracy 3.3 V or 5 V ratiometric bipolar Hall effect sensor

    2) DRV5057: High accuracy 3.3 V or 5 V digital PWM-output Hall effect sensor

    3) DRV5053: 2.5 to 38 V bipolar output Hall effect sensor

    4) DRV425: Integrated Fluxgate Magnetic Sensor IC for Open-Loop Applications

    The DRV5057 is essentially the same as the DRV5055, but with a PWM output.  The DRV5053 is less accurate, but has a higher voltage range.  The DRV425 is a high precision device that is highly sensitive for use with weaker magnetic fields.

  • 0 in reply to Mitch M
    Prodigy 130 points

    Thanks, Mitch.

    The AC frequency I want to measure is 50Hz/60Hz, where sources are the magnetic field generated by indoor powerlines. In this sense, could you further recommend one particular product for this sensing task? 

    Meanwhile, we plan to use an Arduino or  Raspberry Pi as the backend. Could you let us the sensors' compatibility to them?

  • 0 in reply to Xiaoxuan Lu
    TI__Mastermind 26395 points

    Hello,

    The specific part to use depends on a few things, including the strength of the magnetic field you expect to see and the precision you want.

    Most likely you will want the DRV425, especially if you expect a very small magnetic field. From the above parts, this one has the fastest sampling frequency (47 kHz).  This device is also the highest precision and highest sensitivity (±2mT).  The DRV425 is also fairly consistent over temperature.  However, this is also the most expensive of the devices. 

    The DRV5055 is less expensive and still highly accurate, however, the highest sensitivity option is ±21mT, which may not be sensitive enough for you, based on how much magnetic field you expect to see. This device runs at 20 kHz, which is slower than the DRV425, but still may be fast enough for you. This device also has a temperature sensitivity compensation for magnet temperature drift, which will not be good for your application if you expect a lot of temperature changes.  

    If the specs for the DRV5055 work for you, but there is a large distance between the device and the MCU, then you may want to use the DRV5057, which has a PWM output.

    The DRV425 and DRV5055 both have an analog output, so you may need an ADC to use these with your MCU (unless the MCU already has a good ADC on board).  The DRV5057 is PWM output, so the signal can go directly to the MCU, but the signal will need to be decoded.