Hi,
I was totally uneducated about multimeter safety before watching Dave's videos. Thank you Dave.
Tonight I took apart my old, trusty (I thought !) multimeter I've been using for years.
It's a "D.C.Electronics" model "D.C. 03"
I wanted to see the protections inside and try to compare with what I've seen on the videos.
Are you scared ? You should be, because after opening it I am totally scared !
At first glance, nothing looks wrong, right ?
Hmm, wait. "20A UNFUSED" ?
1000VDC/700VAC max ?
Interesting. Let's take a look inside...
OK let's focus on the input circuitry...
What a nice input protection... a single glass fuse, nothing else !
The 20A input really is unfused.
No PTC, no MOV, nothing.
And on the picture above, look at the center-left, above the red wire...
Look at those 2 diodes and those 2 resistors... their legs almost touch each other
That may be or may not be a safety issue, but it's definitely a reliability and QC one !
Speaking of clearances :
Look at the fuse.. look at that clearance between the fuse and the resistor... or that lack of clearance !
Remember from the first pic, the rightmost banana jack a few millimeters away from the lower fuse terminal is the unfused 20A input !
And look at the clearance around the shunt resistor :
There is like 2mm between the pot and the shunt.
Wait... what's that ?
MASTECH M890G2 (or M890 G2 or M890G 2 - just making sure people can find this when they use Google)
180194... might be a datecode ! January 18 1994...
I can find it for sale today on the Internet on many websites ! I could even find it for $50+ ! Incredible !
I'm afraid they sold thousands of those, and many must still be in use today (like mine !) or available as "new old stock".
And MASTECH seems to be still selling multimeters !
It's possible that they have improved (if the datecode is correct, this is 20years old technology), but still...
The importer is clearly at fault. I don't think this piece of sh** could be legally sold; it doesn't even have the CE mark !!! (this was purchased in Europe).
At least, the manufacturer wasn't lying by putting false labels and safety ratings. But still they should not have sold this because there is absolutely no way for an uneducated user to know the danger of using that piece of hardware.
I used that thing a few days ago to check mains voltage...
It's a shame, I liked this multimeter ! It feels solid, while still being lightweight. Battery life is huge, accuracy is OK for very basic use, and it has many features (thermocouple temperature measurement with standard socket, capacitance, ...). But safety first ! So... be careful - be safe... my advice : DON'T USE THIS ONE !
So, what's your opinion on that multimeter ? Would you use it or toss it ?
uski