Author Topic: Wierd looking Shunt....  (Read 3567 times)

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Offline groovesonshuntTopic starter

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Wierd looking Shunt....
« on: December 20, 2022, 12:05:39 pm »
Some time ago, I got myself a Monacor DMT-4010RMS Multimeter. (Danish Company)

After some time, the display would flash at the Volt setting when I came close to touching it. I then opened it up, and found evidence that it had been tampered with. The Shunt had big balls of solder and deep grooves, solder splatter, fingerprint on the inside of the display.
I have only taken apart the main cover into the fuses, so it would not warrent the guarantee.

Have anyone seen grooves on a Shunt like this before?

I got a new one sent back to me, but it started to make the same flashing display error as the first one. Opened it up and found the same grooves on the Shunt. Maybe there is some dirt on the traces, behind the selecter wheel, but I don't want to take it further apart due to the warranty.
The COM test probe also had a smaller size plug, and had a hard time making contact. Worked fine with another set of probes.
 

Offline srb1954

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Re: Wierd looking Shunt....
« Reply #1 on: December 20, 2022, 12:09:04 pm »
Maybe the nicks in the wire and the solder blobs are a crude way of adjusting the shunt resistance to bring it into spec.
 
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Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #2 on: December 20, 2022, 12:14:59 pm »
These are the probes from the new meter.
 

Offline Slh

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Re: Wierd looking Shunt....
« Reply #3 on: December 20, 2022, 01:21:59 pm »
The solder blobs are weird but the nicks are not.

Current shunts are often adjusted by trimming them mechanically. You find it on all sizes. Smaller resistors might be be laser trimmed but it's the same thing really. Make all of them fractionally under spec and cut them to increase the resistance until it's within spec.
 
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Offline BillyO

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Re: Wierd looking Shunt....
« Reply #4 on: December 20, 2022, 02:20:38 pm »
The solder blob is there to fix a nick that was cut to deep.

I prefer filing the shunt.  Much better for getting a precise adjustment but it does take a little longer.
Bill  (Currently a Siglent fanboy)
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Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #5 on: December 20, 2022, 02:48:36 pm »
here is how the meter is acting and a few other observations....



 

Offline BillyO

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Re: Wierd looking Shunt....
« Reply #6 on: December 20, 2022, 02:52:34 pm »
Good lord!  That's atrocious!  They certainly have some serious production issues.

Can you get your money back?  Then get yourself a Brymen or even a UNI-T.

Edit: It seems they are actually a German company out of Bremen.  That looks suspiciously like a stenciled cheap Chinese meter.

If you don't mind y asking, how much was it?
« Last Edit: December 20, 2022, 02:58:01 pm by BillyO »
Bill  (Currently a Siglent fanboy)
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Offline Fungus

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Re: Wierd looking Shunt....
« Reply #7 on: December 20, 2022, 02:55:10 pm »
Have anyone seen grooves on a Shunt like this before?

Yes. That's how they calibrate shunts.

(you bite the shunt with a pair of cutters and it increases the resistance a bit)
 
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Offline BillyO

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Re: Wierd looking Shunt....
« Reply #8 on: December 20, 2022, 03:02:49 pm »
It looks like it sells for about $150 Euro.  That is way too much for a 3.5 digit meter, especially one with such terrible build.
Bill  (Currently a Siglent fanboy)
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Online coromonadalix

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Re: Wierd looking Shunt....
« Reply #9 on: December 20, 2022, 03:09:20 pm »
one brand to avoid ?      they look like the CEM brand
 
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Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #10 on: December 20, 2022, 03:43:13 pm »
one brand to avoid ?      they look like the CEM brand

It sure does!
 

Offline AVGresponding

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Re: Wierd looking Shunt....
« Reply #11 on: December 20, 2022, 03:44:29 pm »
Very much like a rebadged CEM DT9961
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Offline BillyO

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Re: Wierd looking Shunt....
« Reply #12 on: December 20, 2022, 03:51:57 pm »
Very much like a rebadged CEM DT9961
Yes.  Which is a $40 meter.
Bill  (Currently a Siglent fanboy)
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Online coromonadalix

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Re: Wierd looking Shunt....
« Reply #13 on: December 20, 2022, 05:22:12 pm »
 :-DD :-DD :-DD :-DD
 

Offline Stray Electron

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Re: Wierd looking Shunt....
« Reply #14 on: December 20, 2022, 05:46:34 pm »
The solder blobs are weird but the nicks are not.

Current shunts are often adjusted by trimming them mechanically. You find it on all sizes. Smaller resistors might be be laser trimmed but it's the same thing really. Make all of them fractionally under spec and cut them to increase the resistance until it's within spec.

  Exactly.  It's not at all hard to find large external current shunts have been filed.  In urgent situations I have filed resistors to raise their value.  In one company that I used to work for, a production line shutdown costs the company $60,000 per hour so you did anything that you had to in order to get a machine up and running again A S A P.  In that case I eventually got a complete replacement circuit board and I kept it on hand but the old board with the modded resister never failed so I never swapped it out.

   I think the poster that said that it had been filed too deeply and that they soldered up the notch and filed a new one is most likely correct.
 

Offline Fungus

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Re: Wierd looking Shunt....
« Reply #15 on: December 20, 2022, 06:11:34 pm »
I think the poster that said that it had been filed too deeply and that they soldered up the notch and filed a new one is most likely correct.

If it has solder and bite marks then the calibrator was having a bad day.  :-DD
 

Offline Gyro

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Re: Wierd looking Shunt....
« Reply #16 on: December 21, 2022, 11:50:03 am »
I wonder if the solder blob is where they squeezed the cutters a bit too hard and actually cut through!  :D

Yes, the better quality shunts are filed or ground over a long length for uniform dissipation and accuracy. They also have crimped areas near the ends to ensure that they sit at a predictable height (wire length) above the PCB. Fluke are probably best (in a handheld anyway), they weld a U shaped piece of wire across each end of the shunt so that they can do proper 4 wire Kelvin sensing.
Best Regards, Chris
 
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Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #17 on: December 21, 2022, 12:40:25 pm »
Good lord!  That's atrocious!  They certainly have some serious production issues.

Can you get your money back?  Then get yourself a Brymen or even a UNI-T.

Edit: It seems they are actually a German company out of Bremen.  That looks suspiciously like a stenciled cheap Chinese meter.

If you don't mind y asking, how much was it?

Yes, I will get my money back. I paid 120 US, and now its at 178 US.

https://elektronik-lavpris.dk/p116583/dmt-4010rms-digital-multimeter-dmt-4010rms-professionel/
 

Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #18 on: December 21, 2022, 12:51:23 pm »
https://www.monacor.de/

They have the exact same meter on the front page, lower down.
 

Offline RoGeorge

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Re: Wierd looking Shunt....
« Reply #19 on: December 21, 2022, 01:25:57 pm »
The Shunt had big balls of solder and deep grooves

That's shunt tuning for calibration.  Dents make the shunt resistance higher, blobs of solder make the resistance lower.

Offline AVGresponding

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Re: Wierd looking Shunt....
« Reply #20 on: December 21, 2022, 03:00:36 pm »
Good lord!  That's atrocious!  They certainly have some serious production issues.

Can you get your money back?  Then get yourself a Brymen or even a UNI-T.

Edit: It seems they are actually a German company out of Bremen.  That looks suspiciously like a stenciled cheap Chinese meter.

If you don't mind y asking, how much was it?

Yes, I will get my money back. I paid 120 US, and now its at 178 US.

https://elektronik-lavpris.dk/p116583/dmt-4010rms-digital-multimeter-dmt-4010rms-professionel/

That's a very disappointing pricing policy. Are they considered a reputable company, otherwise?
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Offline Neomys Sapiens

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Re: Wierd looking Shunt....
« Reply #21 on: December 22, 2022, 02:05:27 am »

Edit: It seems they are actually a German company out of Bremen.  That looks suspiciously like a stenciled cheap Chinese meter.

That is exactly what 'Monacor' does. Since about 40years. Throwing the cheapest and crappiest electronics at customers mainly in the German speaking area. Although there are exceptions. Their dipmeter was not much worse than the other eastern makes and they sold a simple resistance decade with slide switches for 50.- when even the 'NBN' range of mini-decades did not exist for 10years. You have to look at least twice at everything bearing that name. The only multimeter that I've seen from them until now was such an Volts, Ohms, and DC250mA thing with jacks that were neither 2.3 nor 2mm. Yuck. But round here, known yuck.
 
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Offline groovesonshuntTopic starter

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Re: Wierd looking Shunt....
« Reply #22 on: December 26, 2022, 08:51:18 pm »
In one of Dave's videos 12 years ago, he showed a meter from Extech that looks very familiar to the Monacor...if not the same.
He was also not very impressed with the board layout, or the meter in general. So many things wrong with it.

 

Offline Wrenches of Death

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Re: Wierd looking Shunt....
« Reply #23 on: December 27, 2022, 04:09:25 am »

If it has solder and bite marks then the calibrator was having a bad day.  :-DD

I've seen the dyke bites in shunt wires for decades, but this is the first I've seen of the solder blobs. It doesn't take much imagination to visualize the value changing each time it got warm enough to soften or melt the solder.

WoD

 

Offline AVGresponding

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Re: Wierd looking Shunt....
« Reply #24 on: December 27, 2022, 10:27:32 am »

If it has solder and bite marks then the calibrator was having a bad day.  :-DD

I've seen the dyke bites in shunt wires for decades, but this is the first I've seen of the solder blobs. It doesn't take much imagination to visualize the value changing each time it got warm enough to soften or melt the solder.

WoD

It's called "adaptive resistance"   :popcorn:
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