Mastech MS8218 review

[cyteen]

In these temperature related stress test the result is always determined by the method of the providing the voltage reference. Does it have software compensation or the cheap trick of using two resistors with inverse temperature coefficients so as they drift they do so in opposite directions.

The cheap chinese meters seem it omit the external voltage reference either from the design or (as is the case with the Unit-t UT61E) just off the pcb even when the footprint is already there.   

May be after your initial tests of the UT61E you could mount an LT1790 in U4 and redo the test. There doesn't seem to be that much wrong with the meters design but price constraints mean that if you want accuracy and input protection you expect from the western instruments you'll have to add the parts yourself.

[SeanB]

At 12V almost any fuse will do, not enough arc energy to worry about. The issues come with voltages able to put a lot of energy into the arc. Direct across mains, where the voltage is enough to sustain the arc, and the instantaneous current is able to go to the hundreds of amps to power it during the arc breaking interval. There you need the ceramic body able to contain the pressure, and the fine silica sand to absorb the arc energy and quench the arc by splitting it up.

[MJLorton]

In these temperature related stress test the result is always determined by the method of the providing the voltage reference. Does it have software compensation or the cheap trick of using two resistors with inverse temperature coefficients so as they drift they do so in opposite directions.

The cheap chinese meters seem it omit the external voltage reference either from the design or (as is the case with the Unit-t UT61E) just off the pcb even when the footprint is already there.   

May be after your initial tests of the UT61E you could mount an LT1790 in U4 and redo the test. There doesn't seem to been that much wrong with the meters designs but price constraints mean that if you want accuracy and input protection you expect from the western instruments you'll have to add the parts yourself.

Interesting, I will try to remember to keep an eye open for that when I have the UT61E in my hands.
Thanks for the post.

[MJLorton]

At 12V almost any fuse will do, not enough arc energy to worry about. The issues come with voltages able to put a lot of energy into the arc. Direct across mains, where the voltage is enough to sustain the arc, and the instantaneous current is able to go to the hundreds of amps to power it during the arc breaking interval. There you need the ceramic body able to contain the pressure, and the fine silica sand to absorb the arc energy and quench the arc by splitting it up.

Thanks SeanB....I'm certainly a little wiser after reading your post.

[Mr Eastwood]

Great video!  I was quite interested in this one, but the no temp, plastic locking nuts and the inside board just put me off. :-)

[Kiriakos GR]

Lets turn this conversation in to an educational one, I did one weird thing today,
a tear down of BUSS and SIBA 1000V HRC fuses, and it is sticky topics at my forum.

Inquiring minds want to know if $2.22 USD + free shipping for 3 (three) fuses are of the same quality.

http://www.ebay.ca/itm/360490914215

500V 10A

The "intended" use, at least for me, is low power DC circuits (< 12V DC).  I would put one in a "current measurement only" multimeter and if it blew, no big deal.

PS. Those a great photos and thanks for the teardown.

Thanks mate,
those are HRC fuses for electrical motors, which are very slow in comparison with the "super fast ones".
I have many of those.

[DaveXRQ]

kiri, they placed the wrong fuses in it it's supposed to be a 6.3x32

Are you get payed by Mastech ?
I know that I sound harsh but in this subjects there is no room for jokes or excuses.

If another truly serious company had made an such a mistake, it would be at 9:00 o'clock TV news.

My personal Blog are watched by the Greek federation of unions of electricians contractors,
such news they do interest them allot.

What's wrong with that? Why do you bash about a meter that works properly unlike the similarly priced UT71E?
Try getting a new fluke for 150$ and report back, they won't even have 0.03% accuracy.

[Kiriakos GR]

kiri, they placed the wrong fuses in it it's supposed to be a 6.3x32

Are you get payed by Mastech ?
I know that I sound harsh but in this subjects there is no room for jokes or excuses.

If another truly serious company had made an such a mistake, it would be at 9:00 o'clock TV news.

My personal Blog are watched by the Greek federation of unions of electricians contractors,
such news they do interest them allot.

What's wrong with that? Why do you bash about a meter that works properly unlike the similarly priced UT71E?
Try getting a new fluke for 150$ and report back, they won't even have 0.03% accuracy.

High price point / Fuse issue / slow sampling for such high counts / internal construction / all of those details came to light due this video review.
Bashing ?  SAFETY FIRST !! all the other issues haves a much lesser value.   

[DaveXRQ]

Safety first? You've gotta be kidding me. Replace the damn fuses are you are GOOD TO GO. Understand? I said it a couple of times. REPLACE THE DAMN FUSES.
And once again, nobody pays me to make biased comments. I only make unbiased comments.
A fluke's only good for safety and that thinking of mine has gone to Agilent. well then what fluke do we have at 150 bucks (My currency!)? A fluke 115! And that's a whole 100 bucks more!
Bloody hell that thing doesn't even have a current range

[Kiriakos GR]

Read and learn .... Except if you have credentials to prove that you are some sort of an expert.



The protection should not be subject only to fuse rating but also to PCB track layout and other factors. The conformity should not be only to fuse rating. The conformity should be checked by the multifunction tests of IEC61010-1 2nd Edition Clause 16.2 as followings.
---------------------------------------------------------------------------------------------------------------------------------------------

Multifunction meters and similar equipment shall not cause a HAZARD in any possible combination of RATED input voltages, and settings of function and range controls. Possible HAZARDS include electric shock, fire, arcing and explosion.
Conformity is checked by the following test.


The maximum RATED voltage specified for any function is applied to each pair of TERMINALS in turn, in every combination of function and range controls. The test source connected to the equipment measuring TERMINALS during this test is limited to 3,6 kVA for measurement category I or measurement category II. For measurement category III or measurement category IV, the test circuit has to be capable of delivering 30 kVA.

[retiredcaps]

For those interested in this multimeter, it is also being sold as the Protek 6500.

Right now on ebay, there are a couple of interesting auctions for one that works and one that needs repairs (see pictures of obviously leaked batteries).

This could be a good deal for those who want this multimeter at a reduced price.  Obviously I can't vouch for the sellers or the condition of the multimeters so caveat emptor.

If someone buys the "parts" Protek and manages to fix it, please post how you did it with teardown pictures.

PS. I have no interest in this meter at the current ebay prices.  If I got a broken one for $10, then I might buy one.

[steve30]

Just for the record, since I won this multimeter off Martin a while back it has been pretty good for my electronics use. It is actually quite nice to use, and the construction quality is certainly adequate. I probably wouldn't trust it for CATIII, but I'm not going to use it for that anyway.

What I do find peculiar is the surface mount capacitors inside. They can be seen at the top in Martin's photo; http://mjlorton.com/forum/index.php?action=dlattach;topic=108.0;attach=313;image

Some of them are stacked on top of each other, and some are seriesed and paralleled. Are they all like this?

I'm also curious to know about the crusty components, including the strange looking current shunt. Are they all weird? Or is it just this one? Accuracy on the 10A range seems reasonable.

[retiredcaps]

Some of them are stacked on top of each other, and some are seriesed and paralleled. Are they all like this?

C4 doesn't inspire a lot of confidence that the multimeter will survive a drop because it doesn't look like there is a pad on the "triangle" part?

[steve30]

Nah, they've just soldered two in series and soldered them in parallel with another two parallel caps.

TBH it does look reasonably sturdy though.

[retiredcaps]

Nah, they've just soldered two in series and soldered them in parallel with another two parallel caps.

TBH it does look reasonably sturdy though.

Obviously, you have the unit in front of you so you are in the best position to tell.  I can only judge from the photos.

If the seller for the "parts" MS8218 starts a new auction at 99 cents, then I might be interested ...