Author Topic: Bad luck with my new multimeter (CEM DT-9989)  (Read 5380 times)

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Offline kultakala

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Bad luck with my new multimeter (CEM DT-9989)
« on: January 14, 2017, 07:41:50 pm »
Hi,

Just wanted to post my experience in buying a CEM DT-9989.
I was looking for a second multimeter, maybe a successor for my good old Siemens B1026 Multimeter.
The light does not work anymore, the display itself has not the best contrast for my eyes and...  doesnt matter, something new was needed :)

After reading and comparing a lot of multimeters i liked the idea to get one with a basic oscilloscope in it.
I dont really need an oscilloscope and because i have no permanent workplace and not really enough room to stow away a real oscilloscope i decided to get the DT9989.
But i was a little bit sceptic about it.

I ordered one directly from CEM in germany and when i got it i was really pleased.
The haptic and feel, the display...  the whole device was really good.
But...  it had a dark spot on the display, maybe a little piece of plastic stuck to the display inside the device.
Shaking and tapping did not do anything. Because it was so obviously visible i decided to send it back.

So i got another DT-9989 from a german reseller and it had no such piece of something on the display, tadaaa..
But it had no protective sheet on the display and the way the cables was tied together showed me that it was used already.
The device itself looked very good.
But one of the crocodile clamps (is this the right word ?) was broken.

And while testing it the Ohm resistance range behaved very strange. Sometimes everything was good, sometimes it jumped between OL and some lower values at about 2 Hz and sometimes it stayed at a value between 100 and 200 kOhm.
So the Ohm range has some kind of a loose contact.

So i will send back this device, too...  and think about if i should give it a third try  ::)

Maybe i should pass on the oscilloscope and go with a brymen BM869 or something like that.
But i really liked the little oscilloscope although it misses a lot of functions and goes only up to 10 MHz.
But for the small things i do once or twice a year it would be enough i guess.
 

Offline retiredcaps

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #1 on: January 14, 2017, 07:49:53 pm »
sometimes it jumped between OL and some lower values at about 2 Hz and sometimes it stayed at a value between 100 and 200 kOhm.
CEM doesn't have the best quality control or consistent/replicated/manufacturing process.  You can search this forum for CEM and read about it.

The 172K ohm shown with no probes may mean the MOVs are bad.  That is, someone subjected this meter to high voltage or a possible oops moment and returned it.
 

Offline retiredcaps

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #2 on: January 14, 2017, 07:58:00 pm »
The light does not work anymore, the display itself has not the best contrast for my eyes and...  doesnt matter, something new was needed :)
You might consider one of the smaller Brymen meters?  They have large-ish lcd digits and you can enable backlight.  See Dave's BM235

https://www.eevblog.com/forum/testgear/eevblog-bm235-multimeter-dilemma/

Some of Dave's earlier BM235 batches had some contrast problem, but Brymen changed the resistor value as per

https://www.eevblog.com/forum/testgear/eevblog-brymen-bm235-lcd-issues-or-normal/
 

Offline retiredcaps

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #3 on: January 14, 2017, 08:03:15 pm »
The light does not work anymore,
If you want help fixing your light, start another thread and I can try to make suggestions.

Your B1026 looks like a Gossen to me?  A pic at

https://sigrok.org/wimg/2/2f/Siemens_b1026_3.png
« Last Edit: January 14, 2017, 08:06:02 pm by retiredcaps »
 

Offline kultakala

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #4 on: January 14, 2017, 09:57:19 pm »
CEM doesn't have the best quality control or consistent/replicated/manufacturing process.  You can search this forum for CEM and read about it.

The 172K ohm shown with no probes may mean the MOVs are bad.  That is, someone subjected this meter to high voltage or a possible oops moment and returned it.

Yes, i read about the quality...  and saw the teardown video from Jim Conner on Youtube where he found a bit of solder rattling inside.
But i really like the meter after holding it in my hands.

About the ohm range...  sometimes it works perfectly, and even tapping or knocking on the meter does nothing. After switching to a different function and then back it starts showing weird values... 

Edit: I made a short video... unfortunately upright

https://youtu.be/nb5pA-fpOcQ
« Last Edit: January 14, 2017, 10:31:16 pm by kultakala »
 

Offline kultakala

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #5 on: January 14, 2017, 10:35:27 pm »
The light does not work anymore,
If you want help fixing your light, start another thread and I can try to make suggestions.

Your B1026 looks like a Gossen to me?  A pic at

https://sigrok.org/wimg/2/2f/Siemens_b1026_3.png

I have no idea, could be.
Maybe i can try to fix the light...  but a new multimeter i will buy anyways.
I really like high-tech stuff, gadgets of all kind...  if i would have the money and the space i would have a DSO and all other lab stuff just for fun ;)
 

Offline Muttley Snickers

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #6 on: January 14, 2017, 10:46:54 pm »
Send it back and demand either a full refund or that they thoroughly test the intended replacement meter before posting it out otherwise you have full intentions of going to town on their arse publicly, this is completely inexcusable and obviously unacceptable. I certainly wouldn't tamper with or touch any problematic equipment if it was still within the warranty period as you may risk voiding any further support.
 

Offline joeqsmith

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #7 on: January 14, 2017, 11:12:53 pm »
I had just bought a second DT 9939 for home an am pleased with it.   Funny thing is a friend of mine bought one from the same company just shortly after I bought mine.  I wanted to check it over before they started using it.  We pop the back cover and like my first one, the shield was missing.  Further they had cut the spring that connects the PCB to the shield.  I don't mean left it out, I mean cut it!  And why did they do this??  Because someone had installed the antenna upside down and it shorted to the shield!   The fix rather than correct the antenna, remove the shield!   

New spring, added shield and cleaned up some solder joints.  In business.  So I agree that their quality control is in need of help. 

Post how this all works out for you. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline retiredcaps

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #8 on: January 15, 2017, 01:00:28 am »
CEM's lack of quality control started with Dave's $100 shootout back in June 2010, almost 6.5 years ago.  It may have started earlier, but I wasn't interested in electronics or test equipment then.

6.5 years after that video, we are still seeing about hand made modifications, spaghetti pcb layout, components tacked as bodges, poor soldering, etc.  Clearly, no one in upper management or Q/A at CEM cares enough as they still make meters for others for rebranding (think Extech, Southwire, Craftsman, etc).

While premium names like Fluke and Agilent/Keysight also have their problems, they are at least somewhat quick to acknowledge them and fix them for the next revision or generation of meters.  In addition, their manufacturing process also means a meter made on Monday is likely to be the same as one made on Friday.
 

Offline kultakala

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #9 on: January 15, 2017, 06:41:31 pm »
Send it back and demand either a full refund....

Of course i will send it back. Tomorrow it will be on the way back.
Full refund is guaranteed within 14 days for whatever reason, thats the law here when you shop online.
Dont know how that is handled in other countries.

But i am still not shure if i give it a third try, because i really like that meter.

But one thing i am still not shure about is if i should get a meter with a rechargeable battery like the CEM or some of the Keysights.
Because its not unusual for me that i dont use the meter for several months.
My tools like cordless screwdriver dont have a problem with that, so a multimeter should do it too, right ?
 

Offline Lightages

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #10 on: January 15, 2017, 11:13:04 pm »
Of course i will send it back. Tomorrow it will be on the way back.
Full refund is guaranteed within 14 days for whatever reason, thats the law here when you shop online.
Dont know how that is handled in other countries.

But i am still not shure if i give it a third try, because i really like that meter.

Fool me once, shame on you. Fool me twice, shame on me.

Test equipment is about confidence in the resulting measurement. You have received two faulty units with different faults. That is to say the faults that you have discovered. If they are that unreliable, what other aspects of them are or will be unreliable?

IMHO, better to get something you don't have to question every time you use it.
« Last Edit: January 16, 2017, 03:11:43 am by Lightages »
 

Offline Mitsch

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #11 on: January 16, 2017, 01:37:47 am »
I really recommend to buy a Brymen BM869s, there is only one dealer in germany I think.
Bought my BM257s from there and are very happy with it... They are called welectron.

And maybe you want to add an oscilloscope as well..  ;)
 
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Offline kultakala

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Re: Bad luck with my new multimeter (CEM DT-9989)
« Reply #12 on: January 16, 2017, 08:46:23 am »
I am hesitating ordering the third one...  maybe i will go for a brymen and will get a real oscilloscope later...  i will open a new thread for that.
 


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