2
\$\begingroup\$

I'm working on making improvements to an old project I helped design. The project used an Arduino to take measurements from six sensors to measure the strength of a nearby electromagnet that generated 10 teslas. Now, for this new version, I'm trying to see what kind of improvements that can be done about it hardware-wise based on the feedback from the team.

We previously used the HMC5883L magnetometer for the kit, but we're trying to look into replacing it. For one, it's outdated, and Adafruit doesn't sell it anymore. Another thing, we ran into an issue regarding that sensor. According to the team lead, they had to re-calibrate the sensors every hour because they got saturated due to the strong magnetic field.

After much discussion my team needs a new sensor that won't saturate in that 10 tesla field. Rather, the sensor needs to be stable within two gauss or more (0.2 milli-teslas) and can handle the 10 tesla field. It doesn't have to measure up to 10 teslas, but it has to continue working in that field without any degradation or damage. Most of the magnetometers I seen on Sparkfun and Adafruit seem to be able to measure greater than two gauss, but is it realistic to expect that they can safely operate within 10 teslas, or would it be better to look at individual hall-effect sensors and not these ICs?

\$\endgroup\$

closed as off-topic by Trevor_G, RoyC, Andy aka, Dave Tweed Jan 28 '18 at 13:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Wondering if magnetic fields get old.... \$\endgroup\$ – Trevor_G Jan 25 '18 at 19:55
  • 1
    \$\begingroup\$ ... or maybe drunk \$\endgroup\$ – Andy aka Jan 25 '18 at 20:05
  • \$\begingroup\$ @Trevor_G Sorry about that. \$\endgroup\$ – user101402 Jan 25 '18 at 20:08
  • \$\begingroup\$ LOL don't apologize.. that's just the way my weird brain works. \$\endgroup\$ – Trevor_G Jan 25 '18 at 20:22
  • \$\begingroup\$ can you elaborate on the magnet's pole separation? And pole diameter? Just how much room do you have to play with? A gaussmeter using hall-effect probe can be quite small (that's what we used in a 10T magnet). Those GMR probes are WAY too sensitive. \$\endgroup\$ – glen_geek Jan 25 '18 at 20:55
3
\$\begingroup\$

If the magnetic sensor will saturate they provide reset straps on magnetometers for degaussing. If those aren't working then your exceeding the maximum filed strength of the HMC5883L magnetometer, which is: 8 gauss = 0.0008 Tesla.

The HMC1001 may be more of what your looking for which is good for 10000 gauss = 1 Telsa , but it requires analog electronics (you should be able to find an eval board). By 1 Tesla, I mean if you exceed 1 Tesla, you will ruin the sensor. The acutal range of the sensor is much lower than that, but depends on the gain of the analog electronics.

If you need something beyond that, your probably not going to find it in a magnetometer, because its well outside the range people normally want to sense in.

Either place your magnetometer further away from the electromagnet and use the set/reset straps to degauss it (you have possibly ruined the ones you have).

Look at hall effect sensors, they are better at this kind of thing and some work above 10 Tesla.

I believe that most of honeywell's and other earth magnetic field sensing are Anisotropic Magnetoresistive sensors which only sense to ~100Gauss or 0.01T. However, they are generally more sensitive;

For a sensor to work in the range you need (purple line below), Hall effect (cheap), Magneto-Optical (expensive) and Search coils will work for your application.

I did find one Giant Mageneto Resistive IC, the ACS70331, but it only works to 500 Gauss (0.05T)

I do also know that Hall effects work past the purple line in the graph (greater than 10T)

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Thanks for your reply. The question is: did it saturate due to the strength of the field produced by the electromagnet? If so, then I can see where the HMC1001 might be beneficial, but if there was a way that we could use something like the MPU9250 and prevent it from saturating, then that would be something to look into. I didn't see any 'reset' straps on the HMC5883L breakout board, so I'm unsure as to what you're referring to. We just reset it in software. I'll look into some hall effect sensors as you said and see if we can use them with our Raspberry Pi. \$\endgroup\$ – user101402 Jan 25 '18 at 20:07
  • \$\begingroup\$ The reset straps are built in, so read the datasheet. The MPU9250 only has double the range of the HMC8553, you need something with thousands of time dynamic range, like a hall effect sensor. A 10 Telsa electromagnet will easily ruin magneto resistive bridge sensors, unless your placing it far away from the magnet. If you like the answer please upvote and mark as answered \$\endgroup\$ – Voltage Spike Jan 25 '18 at 20:29
  • \$\begingroup\$ Thanks for your reply. I like your answer, but I'd like to wait and see if more answers come in. I don't seem to see a lot of hall effect sensors, but what kind of parameters should I look for in a magentometer? The datasheet for the HMC1001 shows 1 tesla as the max exposed field, but what else would tell me that the sensor would function in 10 teslas? I know the HMC1001 won't work over 1 tesla; I was trying to use it as an example here. Not all datasheets tell of the max exposed field, so I was wondering what other parameters would indicate that it will work at 10 teslas. \$\endgroup\$ – user101402 Jan 25 '18 at 21:05
  • \$\begingroup\$ What that means is it will survive 10T, but it stops sensing and rails out at much lower than that. (see the graph for technologies) \$\endgroup\$ – Voltage Spike Jan 25 '18 at 22:52
  • \$\begingroup\$ Ok, thanks. The graph is really helpful, but if you don't mind me asking, for all these types of magnetic sensors, in terms of measuring the magnetic field, would they all work the same? Some magnetometers label themselves as compasses, and they can work that way either alone or with another sensor. Other sensors, like the ACS70331, label themselves as a current sensor IC. With all of these various labels for a magnetometer, which one would be best suited to detect and measure a magnetic field while remaining stationary? \$\endgroup\$ – user101402 Jan 26 '18 at 14:51

Not the answer you're looking for? Browse other questions tagged or ask your own question.