harvie
Full Member level 1
Hello. In our workshop we have few cheap digital multimeters and from time to time someone manages to accidentaly "measure" current of car battery or something. Usualy these guys are incapable of replacing the fuses after this happens (or even figuring out that it happend and reporting to me). So i have to replace the fuses all the time.
That made me think about installing PTC self-reseting fuses in the multimeter... But i have two concerns. Safety and precision.
Usualy the precision of cheap multimeters is not so great anyway, so i don't mind introducing little error to the game, but i don't want measurements to be completely off...
Safety is different story. Replacing the fuse with PTC might not be so great idea. PTCs rated for 230V (i live in EU) are available for cheap and i rarely need to measure higher voltages (eg. 360V between two phases). Since i mostly work with low voltage DC and ocasionaly check presence of mains voltage somewhere. On the other hand in some cases i've managed to accidentaly short out mains ac through multimeter because i was unaware of ground loop or something... I don't think that "230V" rating of PTCs is meant as 230V AC RMS...
We have isolation transformer, so i can safely experiment with mains AC. So i am able to safely test what happens when i apply mains voltage to PTCs.
So next obvious thing is keeping the real slow-blow fuse and puting PTC in series to protect it. If something goes wrong the real fuse can still blow.
Do you think this will work? How would you solve this problem? (except for denying noobs from using DMM
That made me think about installing PTC self-reseting fuses in the multimeter... But i have two concerns. Safety and precision.
Usualy the precision of cheap multimeters is not so great anyway, so i don't mind introducing little error to the game, but i don't want measurements to be completely off...
Safety is different story. Replacing the fuse with PTC might not be so great idea. PTCs rated for 230V (i live in EU) are available for cheap and i rarely need to measure higher voltages (eg. 360V between two phases). Since i mostly work with low voltage DC and ocasionaly check presence of mains voltage somewhere. On the other hand in some cases i've managed to accidentaly short out mains ac through multimeter because i was unaware of ground loop or something... I don't think that "230V" rating of PTCs is meant as 230V AC RMS...
We have isolation transformer, so i can safely experiment with mains AC. So i am able to safely test what happens when i apply mains voltage to PTCs.
So next obvious thing is keeping the real slow-blow fuse and puting PTC in series to protect it. If something goes wrong the real fuse can still blow.
Do you think this will work? How would you solve this problem? (except for denying noobs from using DMM
