Bench DMM Noise & Stability Comparisons with TestController

[KungFuJosh]

It’s close enough for me.
I still cannot explain though why on one evening I get certain results from my dmmcheck plus with both meters and the next day with the same cabling completely different (worse) results. One measurement was late in the evening and the other the next morning. There must be some sort of external interference?? I know my “Lab” is very noisy anyway, I cannot use any NCV device there for instance, the moment I pick it up it starts to beep immediately, no matter where I point it at.
Also the manual calibration of my scope fails there, I have to take it to another room to make that successful.

To begin to explain it, you need to monitor ambient temperature. In the attached 525 minute test, you can see when the air conditioner turned on in the morning, and how the meters responded.

[KungFuJosh]

I'll do that next time around, and I'll use battery power again, too...

Battery power is definitely better.

Please replace the DMM7510 driver in TC with the one attached. It's a new / better version. SI8 will also be the default, so you won't need to remember to set that.

I haven't released this in the TC thread yet. I need to make one small change that's not related.

Thanks,
Josh

[Martin72]

you need to monitor ambient temperature

Do you use another device for this that's connected to TC?

[KungFuJosh]

you need to monitor ambient temperature

Do you use another device for this that's connected to TC?

Yes. Any DMM with temperature can be used for that. I used a PT1000 connected to the DAQ6510 in the previous screenshot. I keep the probe near the voltage ref.

If I'm testing all the meters on the workbench, then across the room on my desk I have the SDM3055X-E which will at least give ambient room temperature.

Thanks,
Josh

[TylerPeppy]

you need to monitor ambient temperature

Do you use another device for this that's connected to TC?

Yes. Any DMM with temperature can be used for that. I used a PT1000 connected to the DAQ6510 in the previous screenshot. I keep the probe near the voltage ref.

If I'm testing all the meters on the workbench, then across the room on my desk I have the SDM3055X-E which will at least give ambient room temperature.

Thanks,
Josh

As an aside, in the event you don't have another meter or temperature logger and need to find one, you can pick up the cheap TA612C thermocouple loggers on Amazon for about 50$. They work really well for this; I use them for multi-zone temperature logging here and during my product intergrity verification tests at work.

This way, you could put one probe on the voltage reference, and one on each DMM's air inlet.

Tyler

[KungFuJosh]

As an aside, in the event you don't have another meter or temperature logger and need to find one, you can pick up the cheap TA612C thermocouple loggers on Amazon for about 50$. They work really well for this; I use them for multi-zone temperature logging here and during my product intergrity verification tests at work.

This way, you could put one probe on the voltage reference, and one on each DMM's air inlet.

Tyler

The TA612C is already supported by TestController too.

Not suprisingly, thanks to @Flash2b.

[TylerPeppy]

As an aside, in the event you don't have another meter or temperature logger and need to find one, you can pick up the cheap TA612C thermocouple loggers on Amazon for about 50$. They work really well for this; I use them for multi-zone temperature logging here and during my product intergrity verification tests at work.

This way, you could put one probe on the voltage reference, and one on each DMM's air inlet.

Tyler

The TA612C is already supported by TestController too.

Yes, this is precisely why I suggested it. It also runs off USB-C power when plugged in, so no running down batteries! I still reach for this before my 34970A unless I am logging 50+ thermal zones.

Cheap but works pretty well!

Tyler

[KungFuJosh]

There are many other options to log temperature in TC. If you do not mind using a module instead of a meter. No need to use an expensive DAQ6510 for such a simple task.

Of course there's no need, but that doesn't mean it isn't fun to use.

[KungFuJosh]

Are we still in the game of measuring a zero input reference  to determine noise level ?

We want to measure shorted inputs in auto and 10V (or 20V) ranges.

We also want to measure with a 10V reference.

[KungFuJosh]

Cables are annoying. These tests are with a Pomona 1368-A-60.

Pomona is not the best brand in the world, but it's still a clear improvement over the cheapo generic cables I usually use.

Thanks,
Josh

[Kleinstein]

The data with a shorted input still make some sense to compare. However this would be more the range also used for the 10 V (or similar) case.
With most meters the noise is however from the meter reference, and only a little from the ADC that would be measured with a short.

[KungFuJosh]

Here are some short tests on my 34465A.

Thanks,
Josh

[KungFuJosh]

One annoying feature of TC is that the colors of the graphs are use the coloring order of selecting. Therefore on my 2nd screen shot blue en red is reversed opposed to the grid panels.

Well...  Idid not save the data so I l did a rudimentary color swap on the panels.

I select my devices in alphabetical order (the same order they're in the list). Then they usually match, unless another meter is added.

I save my scripts with the custom color panels the same way. If you a different meter, it's really easy to edit or copy and paste the script into something new and customize one time there to match the new test setup.

[KungFuJosh]

True, but my saved preset did not work anymore since I added a suffix to the meters #name in the definition to split the #metadef.

So add the suffix to the script?

I completely change the meters in the script files sometimes. The only time it didn't work was when I forgot to update the IP address. Oops.

[Martin72]

We want to measure shorted inputs in auto and 10V (or 20V) ranges.

We also want to measure with a 10V reference.

So, first a short with Auto Range, then a short with Manual Range 10V/20V (Siglent), then with a 10V reference voltage...
And the remaining parameters?
10PLC? Measurement duration?
Warm-up condition?
Regarding the short-circuit bridge:
For DVC, 4W isn’t needed; I assume a 2W bridge should therefore actually be sufficient—or has anyone tried this before, 2W vs. 4W for DCV?

[KungFuJosh]

We want to measure shorted inputs in auto and 10V (or 20V) ranges.

We also want to measure with a 10V reference.

So, first a short with Auto Range, then a short with Manual Range 10V/20V (Siglent), then with a 10V reference voltage...
And the remaining parameters?
10PLC? Measurement duration?
Warm-up condition?
Regarding the short-circuit bridge:
For DVC, 4W isn’t needed; I assume a 2W bridge should therefore actually be sufficient—or has anyone tried this before, 2W vs. 4W for DCV?

In the OP:

To get started, I'm sharing a couple 2-minute tests, and a 30-minute test. I'll update this post with more as time elapses.

Meter settings:
Range Auto or 10V (or 20V of your meter doesn't have a 10V range).
10NPLC.
1 sample.
No filtering or averaging.
Auto Zero on.
Line sync on if available.

TestController settings:
Grid panel with advanced readouts (see below for setup)
Chart with logging set to 1 second

Thanks,
Josh

PS. Noting environmental variables might be helpful too, especially if they're unstable. My office is currently stable at 24C (air is off).

Warmup time should always be sufficient for the meters being used. If your meter is good at 30 minutes, cool, but hours of warmup is usually better.

Test durations could be 2 minutes, plus whatever intervals you feel like testing. Some specs are for 2-minute stability, so that's worth keeping common. Other things like 5, 10, 30 minutes, or many hours depends on what you're in the mood for.

Thanks,
Josh

[TylerPeppy]

We want to measure shorted inputs in auto and 10V (or 20V) ranges.

We also want to measure with a 10V reference.

So, first a short with Auto Range, then a short with Manual Range 10V/20V (Siglent), then with a 10V reference voltage...
And the remaining parameters?
10PLC? Measurement duration?
Warm-up condition?
Regarding the short-circuit bridge:
For DVC, 4W isn’t needed; I assume a 2W bridge should therefore actually be sufficient—or has anyone tried this before, 2W vs. 4W for DCV?

I was trying this, I will post some results shortly once things are properly organized. I figured 2W was sufficient, and seeing similar results...

[KungFuJosh]

I redone the 10Vref AZ=On 20V range measurement with 2 Yokogawa's 7562

No flatlines  ... at the end there was a cool breeze floating trough my room. Well I think my new definition seems to work 

Seems my "new" GPIB version is less noisy as my "less new" RS232 version.

Nice job. Can you change to SI7 and show the popups again?

It's interesting- the AZ averaging looks similar to Siglent's.

[Salient666]

I'm trying to improve my test setup.. I want to run the Fluke from my bench supply and leave a test like this on for 24 hours.

[KungFuJosh]

I'm trying to improve my test setup.. I want to run the Fluke from my bench supply and leave a test like this on for 24 hours.

You DMM6500 is set to 1 sample, 10NPLC, no filter?

[Salient666]

I'm trying to improve my test setup.. I want to run the Fluke from my bench supply and leave a test like this on for 24 hours.

You DMM6500 is set to 1 sample, 10NPLC, no filter?

No, I cheated.. I had the filter on on 5NPLC. I wanted to see if it they got any closer.

Here is a graph with both at the same settings..
The Keysight clearly wins this one at the moment.

[KungFuJosh]

I'm trying to improve my test setup.. I want to run the Fluke from my bench supply and leave a test like this on for 24 hours.

You DMM6500 is set to 1 sample, 10NPLC, no filter?

No, I cheated.. I had the filter on on 5NPLC. I wanted to see if it they got any closer.

Here is a graph with both at the same settings..
The Keysight clearly wins this one at the moment.

Filter definitely helps. 10NPLC is better than 5NPLC though; at least for my meters. I made some comparison tests.

Try with yours. Filter ON at 1NPLC, 5NPLC, and 10NPLC. Then Filter OFF at 1NPLC, 5NPLC, and 10NPLC.

[Salient666]

A shorter sample, this time from the direct zener voltage of my 1399 reference (Circuit Valley) to prevent temperature fluctuations a bit.
Still a 4.5ppm vs 23ppm. I really wonder where that difference comes from. It must be the meter because the volt reference is the same, parallel connected.

[KungFuJosh]

Not all HPAK meters are this good on noise performance. The 34465A seems to be exceptional in the 6.5 digit 10V range.

But, yes, more people post results please.

[Salient666]

Here are my tests with:

- Filter OFF @ 1, 5 and 10 PLC
- Filter ON  @ 1, 5 and 10 PLC

Both the Keysight and Keithley benefit greatly indeed from the filter.

The Keitlhey seems to be made for or tuned at 5PLC.

For those who don't want to look at the pictures:

Keysight @ 1PLC FILTER OFF: PP = 10.98u
Keysight @ 1PLC FILTER ON : PP =   4.05u
Keithley @ 1PLC FILTER OFF : PP = 27.23u
Keithley @ 1PLC FILTER ON  : PP = 10.57u

Keysight @ 5PLC FILTER OFF: PP =  7.38u
Keysight @ 5PLC FILTER ON : PP =  3.61u
Keithley @ 5PLC FILTER OFF : PP =15.04u
Keithley @ 5PLC FILTER ON  : PP =  5.90u

Keysight @ 10PLC FILTER OFF: PP =   4.39u
Keysight @ 10PLC FILTER ON : PP =   2.27u
Keithley @ 10PLC FILTER OFF : PP = 21.45u
Keithley @ 10PLC FILTER ON  : PP =   6.57u