EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: T_guttata on January 24, 2022, 11:47:17 am
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Hi everyone
I'm looking for a gauss meter to measure magnetic flux (primarily DC) in the range of 0-2T. It does not seem there are many options available. I only found 1 device <$150: https://de.aliexpress.com/item/1005002110703476.html?gatewayAdapt=glo2deu&spm=a2g0o.productlist.0.0.fc513ce68ZKPMp&algo_pvid=ddee7cc8-07b1-4a1c-8730-9e1673eef36b&algo_exp_id=ddee7cc8-07b1-4a1c-8730-9e1673eef36b-0&pdp_ext_f=%7B%22sku_id%22%3A%2212000018773179768%22%7D&pdp_pi=-1%3B56.07%3B-1%3B-1%40salePrice%3BCHF%3Bsearch-mainSearch (https://de.aliexpress.com/item/1005002110703476.html?gatewayAdapt=glo2deu&spm=a2g0o.productlist.0.0.fc513ce68ZKPMp&algo_pvid=ddee7cc8-07b1-4a1c-8730-9e1673eef36b&algo_exp_id=ddee7cc8-07b1-4a1c-8730-9e1673eef36b-0&pdp_ext_f=%7B%22sku_id%22%3A%2212000018773179768%22%7D&pdp_pi=-1%3B56.07%3B-1%3B-1%40salePrice%3BCHF%3Bsearch-mainSearch)
Does anybody have experience with this TD8620?
Do you know any alternatives? Maybe a probe which can be used on a DSO?
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2T :)
At 1-2T a 9V battery can become a projectile. So could the connector on the end of the probe. - But you already know this if you are working with 1-2T fields.
I didn't realise any such inexpensive devices existed. I manage a research MRI scanner. B0 = 3.0T. The service engineers use an expensive bench Gauss meter but it doesn't stay here.
Something might turn up on eBay. I found several lab grade instruments on eBay, but none of them have probes!
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Well, I intend to use it to measure permanent magnets, so there is nothing dangerous because the flux is very local… But most devices start >$500…
Hall sensors are used in current probes as well, so I thought there might be a probe available for the use with a DSO.
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I have both the TD8620 gauss meter you linked as well as one listed as TM5100 (https://www.aliexpress.com/item/1005001495918370.html (https://www.aliexpress.com/item/1005001495918370.html)).
I originally bought the TD8620 with 5% accuracy rating, but on arrival it had a wiring issue which caused the probe to not give any readings unless it was held ‘just so’. the vendor wouldn’t help unless I shipped it back so I bought the TM5100 2% accuracy model to replace the TD8620.
Turns out these two models, and from what I can tell, almost all other gauss meter devices in the sub $300 category are based on the same PCB template and just have different button and casing configurations. After using the new one as a template to fix the TD8620, in my testing I’ve found them to be almost identical in reading accuracy. They are both within spec to 5% and 2% respectively. I think they’re made by the same company.
Both units seem to have decent stability over time but that’s an anecdote and I haven’t tested it systematically. However The build quality of the TM5100 is much higher than the TD8620. The case material, the probe stiffness, and general fit and finish is much better. The TD8620 just feels like a toy in the hand and the wiring on the inside in very sloppy. I wouldn’t trust the TD8620 unless I had my other gauss meter to compare it to.
I use my meters for testing small permanent and electromagnetic fields and I’m happy with the job they do.
As an aside, you’ll almost certainly never read above 800 milli Tesla on a permanent magnet with a gauss meter like this. The magnetic strength ratings for NdFeB magnets are for maximum internal fields, as soon as the field has to go through air (ie to get to the probe for a reading) it reduces in measured strength considerably. Though it is of course possible to get above 1T from special arrangements of magnets, like hallbach arrays, and easily above 2T with electromagnets for brief periods; the time period of activity, and the size and homogeneity of the field is the hard part.
There are also some really nice gauss meters available which have 3 axis probes and logging and graphing functions but are in the thousands.
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Also I never did find a DSO gauss meter probe with a decent price to spec ratio so if anyone does come across one please share a link.
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Thanks for your reply.
I came a cross this TM5100 but did not see the difference. I even found another one for a similar price which looks different:
https://de.aliexpress.com/item/1005002283783936.html?spm=a2g0o.store_pc_home.productList_6000469297477.pic_23 (https://de.aliexpress.com/item/1005002283783936.html?spm=a2g0o.store_pc_home.productList_6000469297477.pic_23)
Regarding the accuracy: I wan't to measure the flux density on surfaces. I suppose that it's primarly the quality of the probe which determines the accuracy. If the probe is put directly on a surface but has 0.1mm distance, this can affect the result by more than 5% (i tried for an arbitrary sized cylincer magnet):
https://www.supermagnete.de/eng/faq/How-do-you-calculate-the-magnetic-flux-density (https://www.supermagnete.de/eng/faq/How-do-you-calculate-the-magnetic-flux-density)
I googled a lot regarding how you can calculate the flux density of magnets (rod, cylinder, disk), but it's a highly complex topic and I did not find too much useful. The formula I mentioned is not valid for all types of magnets, but I don't know why and what the actual limit is.
That's why I would like to measure and not calculate it.
Did you came across this probes for the use with a DSO or multimeter?
https://www.wuntronic.de/de/gesamtuebersicht-hallsonden-hallsensoren-mit-analogausgang.html (https://www.wuntronic.de/de/gesamtuebersicht-hallsonden-hallsensoren-mit-analogausgang.html)
From the same manufacturerer there is also a device which looks similar to one of the devices from aliexpress: https://www.wuntronic.de/de/teslameter-gaussmeter-mit-usb-zur-messung-von-restmagnetismus.html (https://www.wuntronic.de/de/teslameter-gaussmeter-mit-usb-zur-messung-von-restmagnetismus.html)
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double post