Someone ask me to buy which dmm, Keysight 34465A or Keithley DMM6500

[HighVoltage]

At the same source, the DMM7510 shows a pk to pk of only 7 uV
But about the same offset of around 27 uV

My observation so far with the DMM7510 and DMM6500 is very good, except this calibration offset.

[hwj-d]

Thank you HighVoltage. I'll take care of it. This comparison gives me hope without having the 7510. My DMM6500 shows an surprising similar result, without having my refs calibrated so far, which I still have to do.

Far behind meanwhile my Keysight 34461A. Without ACAL it shows an amazingly high temperature drift compared to the DMM6500.

[alex-sh]

What do you think about that?

Absolutely DMM6500 - this is what I bought several months ago.
Do not get me wrong, 34465A is an excellent meter. However, purely from GUI perspective DMM6500 is much more refined.
 

[Electro Fan]

There has been some discussion about the feasibility of making simultaneous primary and secondary measurements with respect to relay switching and relay wear - but maybe there is a way around the relay issue....

At about 14:30-15:40 this indicates by being flexible on the selection of a compatible range for the secondary measurement (and I guess by definition the range for the primary measurement too) the relay switching might not be needed for dual measurements. 



Have users found that it is generally practical to find a suitable same-range so you can record both measurements simultaneously without invoking relay switching? 

When you record two measurements at the same time can you then see/review both measurements (with trendlines or table views) at the same time using just the front panel display?

On a related question, what's the longest I or V recording duration anyone has seen on the 6500?  minutes, hours, days?

Thanks, EF

[JxR]

Have users found that it is generally practical to find a suitable same-range so you can record both measurements simultaneously without invoking relay switching? 

Yes, you need to set the current from Auto to 1A or 3A ranges.  This will stop relay switching and was confirmed by Brad at Keithley, and tested personally by myself.  The voltage can be left on Auto range also.

[Electro Fan]

Have users found that it is generally practical to find a suitable same-range so you can record both measurements simultaneously without invoking relay switching? 

When you record two measurements at the same time can you then see/review both measurements (with trendlines or table views) at the same time using just the front panel display?

On a related question, what's the longest I or V recording duration anyone has seen on the 6500?  minutes, hours, days?

Thanks, EF

Yes, you need to set the current from Auto to 1A or 3A ranges.  This will stop relay switching and was confirmed by Brad at Keithley, and tested personally by myself.

Thanks for the super fast reply!  How about the 10A range? - can that also potentially also be aligned with the other measurement?

For example, if you have a power supply that runs at 24V and anywhere from 400mA to 4A, if we aren't too picky about the axis label spans on the graph, would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

[JxR]

How about the 10A range? - can that also potentially also be aligned with the other measurement?

For example, if you have a power supply that runs at 24V and anywhere from 400mA to 4A, if we aren't too picky about the axis label spans on the graph, would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

There is no relay switching using the rear panel 10A input, and with the current range set to 10A.  I just tested @20V with a load from 100mA to 3A.  No relay clicking occurred.  That is the best test I can do on short notice given the ranges you gave.  Basically my power supply is 2x channel 20V, but only can sink up to 3A.  While I could source 6A @ 20V, I don't have anything I can sink the current to get 4A.  Although given that I was on the 10A range on the DMM, I see no reason to assume that this behavior would change at 4A.

[JxR]

...would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

You can only do graphs and trends on the primary measurement.  What ever is set to the secondary measurement has no statistics available as far as I'm aware.  You can of course swap between the primary and secondary measurements at any time, but whatever is set to secondary only gives you the numerical value at that moment in time.

This behavior may be completely different if you had one of those scanner cards to use, but then you are certainly going to be using relays.  You may need to dig into the manual, or see if Brad on the big DMM6500 forum post  can answer your question.

[Electro Fan]

How about the 10A range? - can that also potentially also be aligned with the other measurement?

For example, if you have a power supply that runs at 24V and anywhere from 400mA to 4A, if we aren't too picky about the axis label spans on the graph, would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

There is no relay switching using the rear panel 10A input, and with the current range set to 10A.  I just tested @20V with a load from 100mA to 3A.  No relay clicking occurred.  That is the best test I can do on short notice given the ranges you gave.  Basically my power supply is 2x channel 20V, but only can sink up to 3A.  While I could source 6A @ 20V, I don't have anything I can sink the current to get 4A.  Although given that I was on the 10A range on the DMM, I see no reason to assume that this behavior would change at 4A.

So in general it seems not only feasible but practical to pick a range that should allow simultaneous V and I recordings with no relay switching.  Cool
(I think Keithley should make a video showing this for some plausible measurement values.)

Only 3 questions left

1. Can you see the V and I trendlines on the front panel display simultaneously?
(Keithley should put this in the video too.)

2. How long (minutes, hours, days) can you record V and I?
(Keithley should explain this in more clear detail in the spec sheet.)

3. How noisy really is the fan (how many dB at 1 meter distance?)
(Keithley should publish this spec if they haven't already.)

Thanks

[JxR]

1. Can you see the V and I trendlines on the front panel display simultaneously?
(Keithley should put this in the video too.)

No, only the primary measurement has graphs and trends.

2. How long (minutes, hours, days) can you record V and I?
(Keithley should explain this in more clear detail in the spec sheet.)

You can't record both simultaneously.  At least not without a scan card, and then you would be using relays. You could record indefinitely as far as I'm aware, but you might need to use KickStart, and set a sample rate that doesn't exceed the transfer rate over ethernet.  For the internal buffers, it would just depend on your settings and buffer sizes.  I expect you could make settings to record for days on the internal buffer only, but I have never tried it.  You can set measurement delays, count, and sample rate.  Just so you don't want a ridiculous sample rate you can probably stretch it out for a good long while.

3. How noisy really is the fan (how many dB at 1 meter distance?)

I have no equipment to tell you this.  I can hear it.  It is a pretty faint background hum.  It is low enough in volume that I could honestly forget its on, but loud enough to notice the difference when I turn it off.  It certainly doesn't bother me, or is it at a frequency that is irritating to me.  Anyways, I don't personally feel like the noise is a problem.  Although, I should clarify that a good portion of my adult life was spent working out of massive server rooms.  I'm pretty tolerant when it comes to background noises.

[Brad O]

...would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

You can only do graphs and trends on the primary measurement.  What ever is set to the secondary measurement has no statistics available as far as I'm aware.  You can of course swap between the primary and secondary measurements at any time, but whatever is set to secondary only gives you the numerical value at that moment in time.

You can graph the secondary measurement.  Secondary measurements are written to defbuffer2 (you must be on defbuffer1 to use secondary measurements) so you go to MENU > Graph > Data > Add defbuffer2 as a trace.  The Statistics swipe screen will only show stats on the active buffer (so the primary measurement), but you can see some buffer stats for the secondary measurement on the graph screen by switching traces.

How about the 10A range? - can that also potentially also be aligned with the other measurement?

For example, if you have a power supply that runs at 24V and anywhere from 400mA to 4A, if we aren't too picky about the axis label spans on the graph, would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

There is no relay switching using the rear panel 10A input, and with the current range set to 10A.  I just tested @20V with a load from 100mA to 3A.  No relay clicking occurred.  That is the best test I can do on short notice given the ranges you gave.  Basically my power supply is 2x channel 20V, but only can sink up to 3A.  While I could source 6A @ 20V, I don't have anything I can sink the current to get 4A.  Although given that I was on the 10A range on the DMM, I see no reason to assume that this behavior would change at 4A.

Correct, relay switching is dependent on the range selected, it doesn't care what the actual measurement is.

On a related question, what's the longest I or V recording duration anyone has seen on the 6500?  minutes, hours, days?

I've digitized at 1MS/s into a Continuous buffer for ~2 weeks.  That's the longest I've done but I believe others have data-logged for longer, at least with integrated measurements, not sure about digitizing.

1. Can you see the V and I trendlines on the front panel display simultaneously?

Yes, the front panel swipe screen will show the graph you've configured on the graph screen, you don't have any ability to edit the graph from the swipe screen though.

How long (minutes, hours, days) can you record V and I?

You're only limited by the size of your buffer and the speed of your measurements.  With a continuous buffer, you can theoretically record forever but you can't keep all the data as it's overwritten.  The KickStart software is a solution for very long term data-logging, writing a script to handle creating csv files automatically is another potential solution.

How noisy really is the fan (how many dB at 1 meter distance?)

This one I don't know, I don't have a dB-meter unfortunately.  It's one of the quieter instruments on my bench, but other people seem to think it's louder than other products in its class.  That's not really a spec we would publish because then we'd have to dB-meter all the instruments in an anechoic chamber.

(I think Keithley should make a video showing this for some plausible measurement values.)

Thank you for the ideas on the videos!  I will add them to my to-do list...

[JxR]

You can graph the secondary measurement.  Secondary measurements are written to defbuffer2 (you must be on defbuffer1 to use secondary measurements) so you go to MENU > Graph > Data > Add defbuffer2 as a trace.  The Statistics swipe screen will only show stats on the active buffer (so the primary measurement), but you can see some buffer stats for the secondary measurement on the graph screen by switching traces.

Wow, that is awesome.  I learn something new about the device every time you post it seems.  Thanks Brad!

[Electro Fan]

...would it be feasible to measure both without the relays to see the trends of both over time, or is the notion of compatible ranges more theoretical than practical?  Thx again

You can only do graphs and trends on the primary measurement.  What ever is set to the secondary measurement has no statistics available as far as I'm aware.  You can of course swap between the primary and secondary measurements at any time, but whatever is set to secondary only gives you the numerical value at that moment in time.

You can graph the secondary measurement.  Secondary measurements are written to defbuffer2 (you must be on defbuffer1 to use secondary measurements) so you go to MENU > Graph > Data > Add defbuffer2 as a trace.  The Statistics swipe screen will only show stats on the active buffer (so the primary measurement), but you can see some buffer stats for the secondary measurement on the graph screen by switching traces.

1. Can you see the V and I trendlines on the front panel display simultaneously?

Yes, the front panel swipe screen will show the graph you've configured on the graph screen, you don't have any ability to edit the graph from the swipe screen though.

Brad, thanks for all the info but I'm still not clear.... the answer to the first question sounds like the 6500 CANNOT simultaneously display V and I in one graph on the front panel display.  The answer to the second question sounds like maybe you CAN display the V and I trend lines simultaneously.

For the use case I have in mind I don't need to edit the graph, just see a graph showing both V and I over some time period of time.  Is this possible or not?  If it's not possible (which I'm guessing is the answer), I think it might be a good feature to add.  It would probably require the ability of the firmware to label time units on the X axis while labeling V units on one side of the graph and I units on the other side of the graph.  Thx

[JxR]

It would probably require the ability of the firmware to label time units on the X axis while labeling V units on one side of the graph and I units on the other side of the graph.  Thx

Ok, I did try this out.  Both traces can be seen simultaneously.  Although, I do not see a scale for both traces simultaneously.  After you add both buffers to the data for the graph, you see both trend lines, but then you have to click which buffer scale shows up on the y-axis (along with its statistical data).  It is literally a single button press to change the y-axis between the two while watching the trend lines display, but there does not appear to be a way to show both scales on separate sides of the y-axis.

Of course since the data is there in both buffers, it would be simple enough to put a graph up in excel or some other program after retrieving the data.  I agree that it would be ideal to have both scales on separate sides of the y-axis.  Regardless it is pretty cool you can get the data from both measurements in the first place.

I personally would like to see this change, and I would like to be able to perform a secondary measurement in KickStart for the DMM app.  This functionality already exists in KickStart for the SMUs, so hopefully they will consider adding it.

[Electro Fan]

You can see the two lines traveling along next to each other so you can see trends - that’s a pretty good start.

If you could post an image from your test that would be cool. 

Below is a quote from hwj-d that describes my impression - the 7500/6500 is a new architecture and it might take a while to mature to meet all the likely use cases but it seems to be built on a very capable foundation.  Plus, Keithley seems pretty open to hear input and participate in discussion with users.  All good.

This dmm has a whole new approach as we know of the previous conventional type with measuring instruments of this type and offers far more possibilities. This gives rise to the problem of the gui developers of casting these into a mould which, on the one hand, must be consistent in terms of its technical possibilities and, on the other hand, must be as conclusive as possible from the user's point of view.

This results in two learning curves
 - for the developers to integrate these comprehensive new possibilities into the matching gui and api,
 - for the user to discover this new concept to make it usable for oneself by sorting out this mistakes despite the imperfect previous named path.

That is the compromise to be entered into, which we have to go together with such kind of measuring instruments.

We remember that gui and programming interfaces of measuring instruments of the previous conventional type have undergone decades of development on both sides.

Another compromise is the much cheaper technical implementation compared to his bigger brother DMM7510.

[JxR]

Ok, here you go.

The test is as follows:

Sweep voltage from 1-10V in 1V increments and 1s steps, then stop
Sweep current from 100mA-1A in 100mA increments every 0.1s (repeated)

In the bottom left corner where you see the name of the buffer is where I click to change between the two scales on the y-axis.  For the actual range of the scale on the y-axis this particular mode is called auto-independent.  There are other range scales you can pick, however whatever scaling system you use is shared between both measurements.  For instance I could turn auto-scaling off and set: minimum at 0V, and 1V increment.  That would then make the current scale the same (0A, 1A increment).  That would have obviously made the blue trace much smaller in scale.

[Electro Fan]

Thanks for doing that and showing the results.

Seems like the core idea - dual measurement trend lines over the same timeframe on one graph with no relay switching - is very doable.  Might be nice if Keithley can provide some added user friendly control over axis increments/spans and (two sided) y axis labels but it looks like the 6500 is close as-is. 

[hwj-d]

...
Of course since the data is there in both buffers, it would be simple enough to put a graph up in excel or some other program after retrieving the data.  I agree that it would be ideal to have both scales on separate sides of the y-axis.  Regardless it is pretty cool you can get the data from both measurements in the first place.
...

Yes, or use the dmm's script/API to develop an app inside, to use it like a watt-meter or whatever.

[Electro Fan]

Seems like in addition to being a great DMM, with TSP and Lua, the 6500 is a gateway drug that puts hardware enthusiasts on the path to becoming software enthusiasts

[tszaboo]

We have a few 34465A and a DMM6500 in the office. Whenever I can measure something with the 34465A, I always choose that. UI is better, the package is smaller, I've been using it for years, trust it.

The DMM6500... Well it can measure really fast. UI is clunky, illogical, it does BSOD sometimes. Readings are not always visible. It is HUGE. But it is also a lot cheaper, and the high sample rate is useful, when it works.
TBH if I would spend my own money I would buy the Keithley.

[Wintel]

Does the DMM6500 can show one more digits, the 7.5th Digits in the STATISTICS screen like Keysight 34465A?

In Keysight 34465A, when enable the MATH -> Statistics function, the screen can display one more digits (the 7.5th Digits) in Average, like Average: +10.000,123 V, does DMM6500 can get the 7.5th Digits in the STATISTICS screen ?

[hwj-d]

Does the DMM6500 can show one more digits, the 7.5th Digits in the STATISTICS screen like Keysight 34465A?

In Keysight 34465A, when enable the MATH -> Statistics function, the screen can display one more digits (the 7.5th Digits) in Average, like Average: +10.000,123 V, does DMM6500 can get the 7.5th Digits in the STATISTICS screen ?

Yes:
(your example, on both instruments only if DCV >=10V and <11V)

[Wintel]

Does the DMM6500 can show one more digits, the 7.5th Digits in the STATISTICS screen like Keysight 34465A?

In Keysight 34465A, when enable the MATH -> Statistics function, the screen can display one more digits (the 7.5th Digits) in Average, like Average: +10.000,123 V, does DMM6500 can get the 7.5th Digits in the STATISTICS screen ?

Yes:
(your example, on both instruments only if DCV >=10V and <11V)

Thanks for your reply.

Would you mind to do one more test? If DCV > 10V, does DMM6500 also can show the 7.5 digits like 34461A?

Because I find some DMM6500 screen, if DCV >10, the Statistics -> Avg: is 6.5 digits only.

[AG7CK]

Picture copied from post above:



On my meter (latest firmware), the average changes from 9.999999 to 10.00000 volt when I let a voltage source drift upwards, and reverts from 10.xxxxx to 9.xxxxxx when the voltage passes 10.0 volt downwards. This is because the print format is 7 digits with variable floating point. This must result from the programmer not knowing the instrument's specifications and it's intended use. No instrument designer would present a 6.5 digit DMM without a 7.5 digit average for 10 volt DC.

A clear sign of the programmer's total lack of knowledge or thinking, is the apparent resolution of Peak to Peak. Since one can assume that this number is a subtraction of Minimum from Maximum with a maximum resolution of 1 microvolt in this meter class' typical 20 bit or so ADC), it's apparent resolution in picovolts (4.884417 microvolt is 4,884,417 picovolt) is meaningless and looks embarrassing. Similar cases can be argued for all values presented.

This screen needs reprogramming.

[AG7CK]

Somone just sent me a message saying that a 6.5 digit DMM must have a 24 bit ADC. OK for me. I withdraw from any discussion. I guess I should have written "20 bit or more ADC".

Anyway: For Maximum = Minimum in the picture above (both presented with 10 microvolt resolution), it seems that Peak to Peak should prima facie be 0. As in: 7.12409 - 7.12409 = 0. Hence, for Peak to Peak to be 4 or 5 microvolt, there must be a microvolt hidden somewhere  That's all I wanted to say.

A nice read for bits, ENOBs, counts and resolution is: http://zone.ni.com/reference/en-XX/help/370384V-01/dmm/resolution_bits_digits/