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DRV5055: DRV5055

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Replies: 3

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Part Number: DRV5055

Hello,

the datasheet for the DRV5055 linear hall effect sensor claims that the sensor can handle unlimited magnetic flux density in Table 6.1, does that mean strong magnets won't saturate the readings and affect accuracy and sensitivity? Also, is there a linear hall effect sensor that can handle a max operating temperature of 250C-300C? We are trying to continuously sense the fill level of molten metals inside a container

  • Abdoul,

    The Absolute Maximum conditions the device can tolerate are specified in table 6.1.  Here, we indicate that the device will not sustain damage within the conditions specified.  

    The device can saturate it's output relative when a strong enough field is applied.  For instance, refer to the BL specification on page 5 of the datasheet.  Here we indicate the maximum field that can be applied without saturating the output for each sensitivity option.

    I'm not sure magnetic sensing will be ideal for your case, however.  250C-300C is a very high operating temperature. If using a Nd-Fe-B type magnet you would be very close to the Curie temperature.  As the magnet heats, the field produced will weaken, but at the Curie temperature the material hits a critical point where the alignment of the magnetic moment of the atoms is lost. I assume you would have to have the magnet move on some sort of float to monitor the relative level of the molten metal.  If the magnet heats too much, or if there is large variation in the temperatures the magnet will be exposed to, you risk the reliability of your measurements.

    You may consider using ultrasound detection as an alternative.  Please refer to the application note below:

    https://www.ti.com/lit/an/snaa220a/snaa220a.pdf

    Another alternative you might investigate would be using one of our inductive sensing devices such as LDC0851:

    https://training.ti.com/simplify-liquid-level-designs-tis-differential-inductive-switch

    https://www.ti.com/lit/ug/tidu736a/tidu736a.pdf

  • In reply to Scott Bryson:

    I believe Samarium Cobalt and Alnico magnets can handle very intense heat up to 350C and 525C respectively. I see, so +/-176 mT would is the widest you have available? 

  • In reply to Abdoul Bah:

    You are right.  Samarium Cobalt does have a much higher Curie temperature.

    Our widest input range in the linear hall sensors is the DRV5055A4-Q1 with +/-176 mT when operating at 3.3 V. The rated operating temperature of the sensor is only 150 C, so you will need to find a way to thermally protect the device. 

    You should also note that the sensitivity of DRV5055 will vary with temperature as well.  See figure 12 in the datasheet.

    Additionally, your magnet will exhibit a weaker magnetic field as temperature increases.  Large variations in temperature can result in significant discrepancies for your measurement. Your application with the molten metal will require careful thought into how temperature will affect each component.  I would recommend if possible that the magnet be as thermally protected as possible as well.  

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