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Online wraper

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Rigol "amazing" service in Europe
« on: August 14, 2013, 02:43:25 AM »
I bought DM3068 6½-digit multimeter from Rigol authorized distributor Lemona that is Lithuanian company but also has one shop in Riga. I used it about 2 weeks before I noticed huge 4 digits offset on AC current ranges. Therefore, I returned it back for warranty repair. Today it arrived back after 3 months and 20 days being away. It was sent to Germany, nothing were repaired there and they tell me that 3-4 digit offset on all AC current ranges and some of the AC voltage ranges is completely within specks. I calculated BTW, it is not. They say that I must look at noise characteristics in 6-2 and 6-3 chapters in the manual (those are DC characteristics BTW). What should I see there that gives 4 digits offset??? The most fascinating thing is mailing between some Lithuanian and German guys which salesman gave to me. They clearly see the problem, German guy says that on his DM3068 multimeter offset is 0 and still they return mine from Germany saying that I’m a dumbass. BTW salesman I spoke with is a good guy and no problems with him, he understands that problem is there, he just transferred me the information. Check the video.


Manual: http://www.rigol.com/download/Oversea/DMM/User_guide/DM3068_UserGuide_EN.pdf
« Last Edit: August 15, 2013, 08:40:10 PM by wraper »
 

Offline madires

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Re: Rigol "amazing" service in Europe
« Reply #1 on: August 14, 2013, 03:22:20 AM »
Do you know the name of the German company?
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Offline tinhead

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Re: Rigol "amazing" service in Europe
« Reply #2 on: August 14, 2013, 03:27:04 AM »
Do you know the name of the German company?

lol
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Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #3 on: August 14, 2013, 03:38:38 AM »
Rigol Technologies EU GmbH  :)
 

Offline [email protected]

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Re: Rigol "amazing" service in Europe
« Reply #4 on: August 14, 2013, 03:48:53 AM »
They clearly see the problem, German guy says that on his DM3068 multimeter offset is 0 and still they return mine from Germany saying that I’m a dumbass. BTW salesman I spoke with is a good guy and no problems with him, he understands that problem is there, he just transferred me the information. Check the video.

You don't show what is really connected to the meter, that makes it look suspicious.

Anyhow, if the salesman is such a good guy, ask for your money back.
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Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #5 on: August 14, 2013, 04:00:08 AM »
You don't show what is really connected to the meter, that makes it look suspicious.
That's just a 30 cm wire shorting voltage terminals. Current terminals are not connected at all. If something makes you suspicious in the email they measured the same things. To return a money Rigol must conclude that multimeter is defective. That sales guy doesn't own this company, so not he decides about that. Anyway I received it only today, will try to write to that German guy from Rigol in the first place I think. BTW Europe and Eastern Europe especially is not a USA where you can just return anything that easily.
« Last Edit: August 14, 2013, 04:30:57 AM by wraper »
 

Offline mariush

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Re: Rigol "amazing" service in Europe
« Reply #6 on: August 14, 2013, 04:39:09 AM »
If you ordered it online and didn't buy it in person, you have 7 or 10 working days to return it to the store no questions asked. It's EU regulation.

Doesn't mean you will get your money back instantly, it may take a couple of weeks to give you refund, and in some cases they may take 10% off or something like that if you don't send it back completely as it came to you (all packaging etc)
 

Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #7 on: August 14, 2013, 04:41:18 AM »
Those 10 working days were 4 month ago...
 

Offline KedasProbe

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Re: Rigol "amazing" service in Europe
« Reply #8 on: August 14, 2013, 05:52:08 AM »
Did you run the self test? (got any error code?)

Are you sure you have the latest firmware version? (I can forward a small DSP update I got to you from Rigol)

This is my screenshot, it shows 0 on all ACI ranges (taken with my program in my other thread)
(nothing connected)

Did you also try to attach a known signal to verify?
« Last Edit: August 14, 2013, 06:11:15 AM by KedasProbe »
Not everything that counts can be measured. Not everything that can be measured counts.
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Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #9 on: August 14, 2013, 06:16:43 AM »
It passes self test. Before I was returning it, I contacted Rigol for the new firmware and it was latest at that time - 01.01.00.01.07.00. Now I searched old emails and actually I received reply about firmware from the same German guy I mentioned  :). I feeded AC signal from DG4062, it's seems to work, shows similar readings like my U1272A. But with such jumping offset it's precision should be like a $20 meter has.
« Last Edit: August 14, 2013, 06:30:29 AM by wraper »
 

Offline KedasProbe

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Re: Rigol "amazing" service in Europe
« Reply #10 on: August 14, 2013, 06:46:26 AM »
I checked the readings that are stored in double precision (in .xdat) for ACI (open) and they are all exact 0.
This would mean that the software is putting them at 0 because it isn't detecting an AC signal.
Have you already tried it in an other room (interference....)
Do you see something if you use dual screen for frequency?

The signal is still jumping around with the DG4062?
If you tell me which settings (above 3Hz) you generate I can do the same test with my DG4102 and tell/show you what I see on it.
« Last Edit: August 14, 2013, 07:16:08 AM by KedasProbe »
Not everything that counts can be measured. Not everything that can be measured counts.
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Online dr.diesel

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Re: Rigol "amazing" service in Europe
« Reply #11 on: August 14, 2013, 06:51:55 AM »
Rigol Technologies EU GmbH  :)

Don't feel left out though, their support here in the States is crap as well.  I tried 3 times to get a firmware update, finally had to turn to the forum to get it, they simply ignored me.

Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #12 on: August 14, 2013, 06:59:53 AM »
I think it's not worth. DG4062 isn't very precise equipment and U1272A also is multimeter of different class with lower resolution and precision. The thing is that I don't need to test anything because problem exists and is very apparent. That offset is out of spec (% of reading +% of range) which is actually only % of range because reading is 0. Topic is about something another, how they managed to decide that this behavior is OK even if it's totally different on German man's multimeter. If I didn't see that email conversation I wouldn't start this topic at all.
 

Offline KedasProbe

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Re: Rigol "amazing" service in Europe
« Reply #13 on: August 14, 2013, 07:20:27 AM »
Since it isn't defined below 3Hz something small (external) could change its behaviour that's why I suggest to prove that it doesn't work in the specified range, or even in an other environment.
Not everything that counts can be measured. Not everything that can be measured counts.
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Offline Electro Fan

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Re: Rigol "amazing" service in Europe (how about in the U.S.?)
« Reply #14 on: August 14, 2013, 09:26:57 AM »
wraper, I hope somehow Rigol rallies some support for you.

On a somewhat related but slightly off topic question - how has Tequipment.net been doing for Rigol users?  Seems like they answer the phone and take orders pretty well and it seems like a popular place in the U.S. for buying Rigol gear.  Anyone here have any reason to need Tequipment.net to get support/service/repairs on Rigol equipment?  Or is there a way to get Rigol support in the U.S. directly from Rigol if you need a repair?  Thx, EF
 

alm

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Re: Rigol "amazing" service in Europe
« Reply #15 on: August 14, 2013, 11:09:13 AM »
Read the datasheet more carefully, especially footnotes 4 and 8 in the AC specs table. This meter is not specified for values less than 1% of range, and is allowed 0.1% of range extra error between 1% and 5% of range. In the 200 uA range you measured 0.11 uA. The RMS of this offset and a 10 uA signal (5% of range) is sqrt(10^2+0.11^2) = 10.0006 uA. It is allowed 0.12 uA error on this range at any frequency, so well within spec. Now for a 2 uA signal (1% of range), the reading would be 2.003 uA, even though it is allowed 0.32 uA error.

My guess is that the performance verification they refer you to tests the AC ranges at 5% and 100% of range (or something close). They probably performed these tests and concluded (like my math shows) that the meter is within spec. The tech support person replied to you did apparently not have enough knowledge to give you the correct explanation, but I see no reason either to suspect a defect meter.

See also a Keithley FAQ about this very issue. The analog AC RMS-to-DC converter (AD637?) is non-linear for low values. They can either remove the offset and have the non-linearity cause errors for higher values, or just ignore the lower 5% and only use the linear 5-100% range. (almost) All manufacturers choose the latter. The Rigol meter offers similar performance to bench meters made in the last thirty years or so in this regard.

If you want superior AC performance at lower ranges, get a meter that digitally samples the signal to calculate an RMS instead of the venerable AD637 analog True RMS AC-to-DC converter. For example the HP/Agilent 3458A and the Agilent 34410A/34411A. Not sure about the recent low-end models. I think our resident Fluke 8846 fanboy also posted some fairly good results from that meter ;).

Edit: You're correct, 0.1%, not 1%. Fixed.
« Last Edit: August 15, 2013, 12:08:57 AM by alm »
 

Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #16 on: August 14, 2013, 11:26:44 AM »
You are right partially, I missed that somehow, while I looked for such footnotes for lowest % actually. Bet there are two things. This meter didn't behave like this for the first 2 weeks and there are no such behavior on other people's DM3068. And there are also such a thing that this meter has lost last 3 digits of resolution (i'm not talking about precision) because they became jumping garbage. And how it can be that half of the ACV ranges have offset but others doesn't.
and is allowed 1% of range extra error between 1% and 5% of range. In the 200 uA range you measured 0.11 uA. The RMS of this offset and a 10 uA signal (5% of range) is sqrt(10^2+0.11^2) = 10.0006 uA.
0.1% of the range extra error, not 1% BTW
« Last Edit: August 14, 2013, 07:54:24 PM by wraper »
 

Offline Owen

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Re: Rigol "amazing" service in Europe
« Reply #17 on: August 14, 2013, 11:59:44 PM »
You've leaved the current jack open... If you take a look at your manual page 33, you'll see the correct way to connect it. Would you please connect it right and than short the probes? Is it right now?
« Last Edit: August 15, 2013, 12:07:12 AM by Owen »
 

alm

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Re: Rigol "amazing" service in Europe
« Reply #18 on: August 15, 2013, 12:28:39 AM »
I assume it was measured with the correct connections and this was just for taking a quick picture.

Are the last three digits only jumping with the terminals shorted, or also when connected to a voltage/current more than 5% of range? Now to find an AC voltage/current source that is stable down to the sixth digit ;).

Does changing the NPLC have any effect on the magnitude of the fluctuations? You should be able to use stats functions to quantify the fluctuations. Just because some meters might be substantially better does not mean that every meter they sell has to be as good. Arguing about fluctuations (that also depend on the source), that it used to work better or works better on other meters is tricky, since this is not generally specified in the spec sheet.

Did you try repeating the measurements in a different physical location (eg. work instead of home)? An external interference source may have appeared, exposing poor EMC.

Why some ranges have offset and others don't: I'm not familiar with its internals, but it may alternatingly switch in an extra amplifier that affects the offset. In my opinion any AC measurement with shorted terminals is irrelevant because I expect an offset for conventional true RMS meters. This offset will not substantially affect the accuracy in the 5-100% range, even if it fluctuates. I don't have a Rigol DMM to test, though.

I fixed the factor 10 error in the offset accuracy, thanks.
 

Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #19 on: August 15, 2013, 01:18:54 AM »
I measured 100mA 50Hz AC current an 2A range. U1272A was connected in series and showed rock solid 100.04 - 100.05mA current in all period of experiment. Rigol showed 0.100,6.. A at the begining, in ~30 seconds it dropped to 0.100,3.. A, then jumped to 0.100.9.. A in couple of minutes. All 3 last digits jumping all the time. This was to prove that it is crap also on >5% range. There is AC filter setting only  for AC on slowest 3Hz it averages jumping in short term but in long term it doesn't help. About different place, guy in Lithuania got the same result. Whatever EMC would be an all ranges (there are couple ACV ranges free of that) and I would need a working magnetron in my room to achieve this. This is 100% a fault because as I said it had not any of these problems in the beginning.
 

Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #20 on: August 15, 2013, 01:28:41 AM »
You've leaved the current jack open... If you take a look at your manual page 33, you'll see the correct way to connect it. Would you please connect it right and than short the probes? Is it right now?
I also tried to short current jacks, that gives nothing. BTW I don't think that shorting 50 mOhm shunt on 2A and 10A range will make any sense.
 

Offline KedasProbe

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Re: Rigol "amazing" service in Europe
« Reply #21 on: August 15, 2013, 02:20:32 AM »
In case you want to compare your device with mine: 5Vrms/27k is about 185µA (1kHz)
(My DM3068 wasn't warmed up)

Notice: that the current isn't high enough for the 200mA range and the DMM firmware decides to make them zero. (you see it did one measurement before making all following values 0)
Then
I increased the 5Vrms to 7Vrms over the 27K resistor and then you see values on the 200mA range (although this is obviously not the range you use for this measurement.)

« Last Edit: August 15, 2013, 02:41:05 AM by KedasProbe »
Not everything that counts can be measured. Not everything that can be measured counts.
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Online wraper

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Re: Rigol "amazing" service in Europe
« Reply #22 on: August 15, 2013, 03:29:37 AM »
Here is a trend on 2A range, 50Hz sine. U1272A daisplayed 100,08mA all the time without any fluctuation. Added trend on 20mA range measuring 2mA for one hour. Current drifted by 0,6 uA in long term but was rock solid on short term according to U1272A. DM3068 readings fluctuate by 5uA. Therefore last 3 digits are not more than fluctuating rubbish on both ranges (4 digits on screenshots because multimeter adds 1 digit to the end and doesn't display the first).
KedasProbe, thanks for measurments.
« Last Edit: August 15, 2013, 07:38:24 AM by wraper »
 

Offline good_cap/bad_cap

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Re: Rigol "amazing" service in Europe
« Reply #23 on: August 15, 2013, 04:05:33 AM »
Be careful with updating the firmware of these DMMs. I got a newer firmware for my DM3061 from Rigol EU Support. After the upgrade, the meter was out of calibration. Afterwards,  they told me that it has to be recalibrated after the update. Since the newer firmware did not solve my problem, I was able to go back to the old one. Luckily, the cal data had not been altered....
 

Offline KedasProbe

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Re: Rigol "amazing" service in Europe
« Reply #24 on: August 15, 2013, 05:07:28 AM »
Be careful with updating the firmware of these DMMs. I got a newer firmware for my DM3061 from Rigol EU Support. After the upgrade, the meter was out of calibration. Afterwards,  they told me that it has to be recalibrated after the update. Since the newer firmware did not solve my problem, I was able to go back to the old one. Luckily, the cal data had not been altered....

Thanks for the warning, how did you know it was out of calibration? did the self test indicate it, did you measure it or was there an other clear indication?

anyone knows if this is also the case for the DM3068?
« Last Edit: August 15, 2013, 05:12:53 AM by KedasProbe »
Not everything that counts can be measured. Not everything that can be measured counts.
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