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I got a DT-9205M multimeter, it has 20A unfused and 0.2A fused after I saw the PCB, surprisingly there is no fuse on the 0.2A and instead of that they put 000 resistors on it

I wonder if I could put a 0.2A fuse my self but I don't know exactly where the right spot is

also, can I replace 000 resistor with a fuse?

enter image description here

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  • \$\begingroup\$ "I wonder if I could put a 20A fuse my self" Pretty sure you mean a 0.2A fuse, not a 20A fuse. I think you're meant to remove the 000A fuse and put in a real fuse on the big terminals. It's just a fuse bypass. \$\endgroup\$ – DKNguyen Aug 15 '20 at 15:34
  • \$\begingroup\$ there is only one place inside the multimeter circuit where you could insert a fuse \$\endgroup\$ – jsotola Aug 15 '20 at 15:42
  • \$\begingroup\$ Honestly instead of putting time and money into this, I'd save up for a better meter. A link instead of a fuse on the low current range? If that's their general attitude towards safety, yikes. \$\endgroup\$ – marcelm Aug 15 '20 at 16:08
  • \$\begingroup\$ In this YouTube video it showns a leaded fuse being used (out of the factory, apparently). \$\endgroup\$ – Andrew Morton Aug 15 '20 at 16:28
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    \$\begingroup\$ @yosober, that is not a 20 A fuse ... besides, there is already a huge, clearly marked space for a 0.2 A fuse \$\endgroup\$ – jsotola Aug 15 '20 at 16:37
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The place for the fuse is the big area marked with white outline, with two metal pads, and the text "FUSE 0.2A/250V".

You can also replace the zero ohm SMD resistor with a fuse if you like.

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  • \$\begingroup\$ Yes the SMD fuses in HDD’s are faster. But using the intended strip located with silkscreen use fast low and tin part and pads quickly before bonding as in SnPb solder \$\endgroup\$ – Tony Stewart EE75 Aug 15 '20 at 15:44
  • \$\begingroup\$ thanks but is this the correct way to put the fuse? sorry for asking a stupid question but I don't know the reason why the shape of one pad is different than the other s11.picofile.com/file/8405785668/photo_2020_08_15_21_00_49.jpg \$\endgroup\$ – yosober Aug 15 '20 at 16:34
  • \$\begingroup\$ Yes, that's correct. You might want to get a fuse holder and solder it to the PCB. \$\endgroup\$ – Justme Aug 15 '20 at 17:26
  • \$\begingroup\$ sorry if I'm asking again but can I put another fuse for 20A? instead of that resistor? is it even related to 20A? \$\endgroup\$ – yosober Aug 15 '20 at 17:56
  • \$\begingroup\$ It's not related to 20A. 20A is unfused, there is no place for it. That multimeter is like $5 one. If you fuse it and it breaks, how many fuses you get with $5? Consider buying a multimeter that already has fuses inside it. \$\endgroup\$ – Justme Aug 15 '20 at 18:21
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If your meter was never made to accommodate a 20A fuse, then there will be no room on the PCB for a 20A fuse. Instead, get a fused probe or make a banana plug to banana jack cable with a fuse in it and put it inline with one of your probes. There are fuse carriers with lead wires that you can do this with.

If you want to add a 0.2A fuse, you can either replace that 000 jumper with a 0.2A fuse with the same footprint, or simply remove it and place a 0.2A fuse across the big pads labelled as such. That little 000 jumper is just a fuse bypass.

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From the comments:

Sorry if I'm asking again but can I put another fuse for 20 A? instead of that resistor? is it even related to 20 A?

R15 is the current shunt. Typically it will be 0.01 Ω so that 20 A gives a 200 mV drop across it and this gives 200 mV to the LCD voltmeter module. (Actually 199.9 mV is the maximum that can be displayed.)

So no, you can't put a 20 A fuse in.

Be very aware that if you take a voltage reading having forgetton to move the leads back to V + COM after taking a current reading that you will apply a short circuit and may create an arc flash. The professional meters will have a special fuse for this circuit and replacement fuses generally cost more than a supermarket multimeter.

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