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Multimeter problem

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whiz115

Member
Hi

Recently i got this...

MS8221A - Digital Multimeter

My problem is that the multimeter is not functioning properly on ACA function..
i've placed the instrument in series with an 6.3VAC 50Hz source and the load.. but i don't get a thing!!!

then i tried to measure the current drawing of an electric fan from the mains and i got that it draws about 0.4A at 220VAC then again i went back to my previous test and still nothing! and now i can't even measure the electric fan!!!! :rolleyes:

what's wrong? should i take the multimeter back to where i bought it?
 

Sceadwian

Banned
Are you using the right ports on the meter? Your 6.3VAC load is going to be on the ma scale which is a different plug from the higher current one.
 
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whiz115

Member
Are you using the right ports on the meter?
yes i also tried the 10A unfused port.

is it possible that i'm doing something wrong?! or the instrument is damaged?? i'm very frustrated because i bought that mastech thing specifically so i can measure AC current!!!
 

Sceadwian

Banned
Are you sure there's actually current going through it? And why 6.3VAC out of curiosity. I have a Mastech meter myself I'm not real pleased with it, because the inductance and capactiance measuring features don't work properly, but as far as a general meter goes it's fine.
 
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Sceadwian

Banned
You sure your tube is working correctly? I mean you've tested the meter on mains AC and it works, are you sure there's current passing?
 

whiz115

Member
You sure your tube is working correctly? I mean you've tested the meter on mains AC and it works, are you sure there's current passing?
yes it works fine but when i put the instrument in series.. then the filaments don't get heated!

only once it worked on the mains,right now it's not working...though the rest of the multimeter functions are fine!!

really crazy.. huh?

is there something i can check inside the multimeter other than the fuse?!
 
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crutschow

Well-Known Member
Most Helpful Member
If the filaments don't light, then it sounds like the meter fuse is blown. You should use the 10A inputs for the filament measurement. The filaments likely draw more than the fuse rating.
 

whiz115

Member
If the filaments don't light, then it sounds like the meter fuse is blown. You should use the 10A inputs for the filament measurement. The filaments likely draw more than the fuse rating.
ofc... they draw about 3A so in that case i'm using the 10A unfused port..

i'm wondering if there is something specific with the ACA function that i can check inside the multimeter other than the fuse?!
 
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Sceadwian

Banned
Both ports on that meter should be fused. Check them. I have an MS8222H, selling a meter with a 10 amp current measure mode that doesn't have a fuse would be stupid. My meter is basically the exact same as yours only mine has an inductor and capacitor testing ability. Mine does have some nice easy to remove 'screws' on the battery door that eagerly shows the fuses.
 
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smanches

New Member
I have a Mas-344 and both it's 400mA and 10A ports are fused. Sounds like a blown fuse to me too.
 

smanches

New Member
Strange to see an unfused port. I'd then say the port is blown.

If it only worked once, then stopped, sounds like something blew.
 

whiz115

Member
Strange to see an unfused port. I'd then say the port is blown.

If it only worked once, then stopped, sounds like something blew.
any help on what to check? because i don't see something damaged inside the instrument.

though i don't see why it should get damaged if it really did!! :rolleyes:
 

Sceadwian

Banned
I'd return the meter, if nothing is obviously damaged then there may have been a spike that damaged the amplifier circuit that reads the voltage from the shunt resistor on the unfused line.
 

crutschow

Well-Known Member
Most Helpful Member
Can you check for continuity through the 10A connection?
 

whiz115

Member
Iif nothing is obviously damaged then there may have been a spike that damaged the amplifier circuit that reads the voltage from the shunt resistor on the unfused line.
what kind of spike?

Can you check for continuity through the 10A connection?
first tried to measure how much current draws from the mains a 12VDC stabilized power supply..
using the 10A unfused port it blew the 200mA/250V fuse!!! :eek:

after i replaced the fuse i tried between the 12VDC power supply output and a small 12V graphics card fan...the fan spins both on ACA function and on DCA function..but on DCA i see "1" which i think it means out of range and on ACA i see "0.32"!
 
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crutschow

Well-Known Member
Most Helpful Member
tested it on 10A unfused port with a 12VDC power supply and a small 12V graphics card fan...the fan spins both on ACA function and on DCA function..but on DCA i see "1" which i think it means out of range and on ACA i see "0.32"
I doubt that the fan takes more than 10A so you shouldn't be seeing an over-range indication.

The fact that you see 0.32 on the ACA range indicates that the meter is working and reading the AC ripple on the fan current.
 

whiz115

Member
hi

i got another multimeter the same model... and i have exactly the
same problem!!! :rolleyes:

i don't know what i did wrong (if i did something wrong...)

here's a photo of the inside of the multimeter there are few ICs one
is an HEF4011b the other says something 062C/EZ805 (probably it's an TL62 op-amp..) and there is also a COB which i guess it is the LCD controller and the other one i don't know what it is...probably it's a custom made Ic.

can somebody tell me which one can be responsible for the problem?

Thanks!!!
 

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crutschow

Well-Known Member
Most Helpful Member
Post a circuit of exactly how you connected the meter and the meter switch setting.
 
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