Author Topic: New Keithley DMM6500 and now DAQ6510  (Read 97737 times)

0 Members and 1 Guest are viewing this topic.

Offline HendriXML

  • Frequent Contributor
  • **
  • Posts: 711
  • Country: nl
    • KiCad-BOM-reporter
Re: New Keithley DMM6500 and now DAQ6510
« Reply #875 on: December 25, 2019, 11:12:03 am »
I used a script that interacts with a triggermodel on the dmm, just like before, but now doing simultaneously the "exact" same reading with a scope.
https://www.eevblog.com/forum/testgear/battery-charging-using-a-siglent-sds1104x-and-spd3303x/msg2842750/#msg2842750
One thing that would be nice if there was a way keep the auto zero off, and do a "zeroing" somewhere in the trigger model, so it doesn't delay the actual measurement. Using the scpi command which does that is not allowed with a running trigger model. Imo it should have an action block for it.

Section 13
pgs 98-99
[:SENSe[1]]:<function>:AZERo[:STATe]

VOLT:AZER OFF   (Turn auto zero off)
VOLT:AZER ONCE  (Perform a single reference measurement)
While a trigger model is running that command is not allowed. Like (i assume) most SCPI commands.
Because of that, the trigger model imo should support it.
“I ‘d like to reincarnate as a dung beetle, ‘cause there’s nothing wrong with a shitty life, real misery comes from high expectations”
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 6764
  • Country: de
Re: New Keithley DMM6500 and now DAQ6510
« Reply #876 on: December 25, 2019, 11:24:43 am »
The problem with zeroing may be more than just a software problem. I would expect a principle limitation from the hardware side: while the zero reading is running this would still need to complete (thus some 20ms). Even if aborted faster it would cause some delay - for a multi-slope ADC it just takes some time to restart. An extra abort of conversion would likely need low level support, so a more difficult part. So I would consider the 20 ms (16.x ms with 60 Hz) the minimum delay one has to expect.

Depending on the application this may be acceptable.
 
 

Offline HendriXML

  • Frequent Contributor
  • **
  • Posts: 711
  • Country: nl
    • KiCad-BOM-reporter
Re: New Keithley DMM6500 and now DAQ6510
« Reply #877 on: December 25, 2019, 11:45:10 am »
So I think having it as an action in the trigger model is a safe solution. An auto function imo should have a manual counter part. For my slow measurements it would be a good solution. Now I'm not sure how much the accuracy drifts in an hour or so. In my case it is just a fun experiment, but I can think of situations where it is critical to measure at the exact same time.
Another solution would be to do the auto zeroing after the actual measurement as an option, but doing that manually would be preferable.
« Last Edit: December 25, 2019, 12:29:52 pm by HendriXML »
“I ‘d like to reincarnate as a dung beetle, ‘cause there’s nothing wrong with a shitty life, real misery comes from high expectations”
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 6764
  • Country: de
Re: New Keithley DMM6500 and now DAQ6510
« Reply #878 on: December 25, 2019, 12:37:09 pm »
Depending on the actual HW used in the ADC, in non AZ mode there can be quite some drift and also low frequency noise (from the OPs, but also the resistors) that is suppressed with the zero reading. So it is not only about hours but already seconds can make a difference. So if time permits the zero reading can be really helpful. Doing the zero reading just after the actual signal could be a really good solution, if one can live with the extra delay for the result. However I am afraid this could be too close to the basics to be supported in the current software - so it may need a updated software. Ideally there would be different versions of the auto zero mode to choose: zero before signal, zero after signal and the current version that is likely doing some interpolation / extrapolations on the zero readings over some time frame.

The zero reading seem to be a tricky topic in the Keithley meters. It looks a little like some of the extra noise seen at the 10 seconds time scale is due to a not so good solution in doing the zero readings or taking the readings into account. This is kind of effecting the very basics of the meter, but it could be worth to get a better solution there. It may not be top priority with the DAQ6510 but a similar weakness shows up in other meters too - so kind of a legacy weakness, possibly dating back to the K2001 or even 19x times.
 
The following users thanked this post: HendriXML

Offline cozdas

  • Contributor
  • Posts: 38
Re: New Keithley DMM6500 and now DAQ6510
« Reply #879 on: December 26, 2019, 05:20:12 am »
I was planning to build a DIY Solid state, 10-chan SCAN card (so that I can collect data during the night at home without the dripping tap simulation), but since DMM6500 seems to drive the 20-chan card I changed my design to double the channels (the more the merrier).

I'll let you know if I hit a problem with the DMM6500 behavior,

It's alive!!!!

I still need to buy more solid-state relays to populate the rest of the board but what's there seems to work flawlessly (so far), silent and fast. Since I was trying to keep the cost as low as possible (you can tell from the all DIY PCB board), the relays are not the best, the on state resistance of each channel is around 2 Ohm. But it's not a big deal as I have plenty of channels to use kelvin connections if needed. A $12 Atmega32u4 based board is handling all the logic.

(top board: Keithley 2000-Scan with wires attached for protocol sniffing)
(bottom board: DIY 20-chan solid state scan card)

I just released the details of this project here for anyone interested in.

Enjoy
« Last Edit: December 27, 2019, 05:22:03 am by cozdas »
 
The following users thanked this post: eplpwr

Offline drummerdimitri

  • Frequent Contributor
  • **
  • Posts: 411
  • Country: lb
Re: New Keithley DMM6500 and now DAQ6510
« Reply #880 on: December 30, 2019, 05:36:24 pm »
I have unfortunately plugged my meter on the 3A front current terminal directly to 220V AC by mistake and it has blown the internal 3.5A fuse but upon its replacement, I am getting a 0.7 A current reading without anything connected t o the 3A terminals (front and rear.)

I tried testing the rear 10A input and that still works fine so not sure what damage that might have caused.

Why did the damage occur in the first place? This is a common mistake and shouldn't damage such a DMM.

What to do now?  :-// |O
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 6764
  • Country: de
Re: New Keithley DMM6500 and now DAQ6510
« Reply #881 on: December 30, 2019, 06:02:25 pm »
The fuse may not allays be fast enough to brake the current path, before doing damage. Beside the high current spike the spark in the fuse could cause trouble from RF interference. Ideally there should be no permanent damage except for the fuse, but it is definitely stressing things.

I first check would be so see if there is still connection in the 3 A range (e.g. a blown shunt or trace).
It could also be worth checking the very low current ranges (e.g. 100 µA).
The next step would than likely be a visual inspection to see if there is visible damage (e.g. blown trace). One could also measure (with a second meter) if there is actually a voltage aver the chain of shunt resistors.

If nothing visible it would likely be time do to some reverse engineering to see which chips are used for the current ranges. As the 10 A range and likely voltage are still working OK, the damage should be quite close to the input side of the current ranges: something like the OP for bootstrapping the protection, MOSFETs used for switching between shunts or the first CMOS switch or amplifier to see the shunt voltage.
 
The following users thanked this post: drummerdimitri

Offline drummerdimitri

  • Frequent Contributor
  • **
  • Posts: 411
  • Country: lb
Re: New Keithley DMM6500 and now DAQ6510
« Reply #882 on: December 30, 2019, 08:57:58 pm »
The fuse may not allays be fast enough to brake the current path, before doing damage. Beside the high current spike the spark in the fuse could cause trouble from RF interference. Ideally there should be no permanent damage except for the fuse, but it is definitely stressing things.

I first check would be so see if there is still connection in the 3 A range (e.g. a blown shunt or trace).
It could also be worth checking the very low current ranges (e.g. 100 µA).
The next step would than likely be a visual inspection to see if there is visible damage (e.g. blown trace). One could also measure (with a second meter) if there is actually a voltage aver the chain of shunt resistors.

If nothing visible it would likely be time do to some reverse engineering to see which chips are used for the current ranges. As the 10 A range and likely voltage are still working OK, the damage should be quite close to the input side of the current ranges: something like the OP for bootstrapping the protection, MOSFETs used for switching between shunts or the first CMOS switch or amplifier to see the shunt voltage.

So pretty much all the 3A connection shunts are not working and there is no visible damage on the board whatsoever.

Voltage and 10A remain fully operational.

I'm not qualified enough to diagnose the issue and conduct the necessary repairs so does it have to go back to Keithley for that? Bought online from RS components by the way.
 

Offline HighVoltage

  • Super Contributor
  • ***
  • Posts: 4379
  • Country: de
Re: New Keithley DMM6500 and now DAQ6510
« Reply #883 on: December 30, 2019, 10:08:25 pm »

I'm not qualified enough to diagnose the issue and conduct the necessary repairs so does it have to go back to Keithley for that? Bought online from RS components by the way.

Keithley would probably make a swap of the main board and not a component level repair.
Would be interesting to know, how much they charge for that.

The repair should be possible and not too difficult.
If you open it up, can you take a few pictures of the input circuitry of the shunts and surrounding area?

 
There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline drummerdimitri

  • Frequent Contributor
  • **
  • Posts: 411
  • Country: lb
Re: New Keithley DMM6500 and now DAQ6510
« Reply #884 on: December 30, 2019, 11:25:03 pm »

I'm not qualified enough to diagnose the issue and conduct the necessary repairs so does it have to go back to Keithley for that? Bought online from RS components by the way.

Keithley would probably make a swap of the main board and not a component level repair.
Would be interesting to know, how much they charge for that.

The repair should be possible and not too difficult.
If you open it up, can you take a few pictures of the input circuitry of the shunts and surrounding area?

Here you go.
 

Offline pmcouto

  • Supporter
  • ****
  • Posts: 96
  • Country: pt
Re: New Keithley DMM6500 and now DAQ6510
« Reply #885 on: December 31, 2019, 07:44:31 am »
K7 doesn't look good...
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 6764
  • Country: de
Re: New Keithley DMM6500 and now DAQ6510
« Reply #886 on: December 31, 2019, 09:10:25 am »
The damage should be one of the more easy repairs, as it should be located very much near the input part.
If not covered by some warranty the repair at Keithley would likely be rather expensive - possibly not worth it, especially as the voltage and ohms ranges still seem to work and shipping may be expensive too.


I don't think K7 is involved. The blob on top looks odd, but this is more like glue to hold the resistor array.

So far I can not see the higher value shunts and identify the relays / MOSFETs used for shunt switching. They may be just left to the fuse under the shield. Only the smallest shunt resistor is visible right next to CR20 (which is the rectifier used to protect the shunts. It is a possible culprit - so one could check the rectifier in circuit for shorts. The DC side of the rectifier could also be a good test point to see which voltage is present there.
 
The following users thanked this post: drummerdimitri, exe

Offline HendriXML

  • Frequent Contributor
  • **
  • Posts: 711
  • Country: nl
    • KiCad-BOM-reporter
Re: New Keithley DMM6500 and now DAQ6510
« Reply #887 on: January 04, 2020, 05:17:22 pm »
As once mentioned I have 2 master power switches to turn off all my devices. My scope has a soft power on/off, just like the dmm, but supports a setting like resume on power on, thus starting when the main switch is activated.
The dmm does not have this function, but I know it will resume when it was active before the master switch is turned off.

The question is: is it bad practice to switch it off using only the master switch. I normally do a shutdown of the device as well, but that seems shutdown immediately, so that it makes me wonder if its needed at all. The manual does not really addresses this.
But because it resumes I even think it might be a supported feature. Any idea's?
« Last Edit: January 10, 2020, 11:29:58 pm by HendriXML »
“I ‘d like to reincarnate as a dung beetle, ‘cause there’s nothing wrong with a shitty life, real misery comes from high expectations”
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf