All about Keithley DMM7510. Bugs and features, recipes, advice, notes.

[MegaVolt]

Hi Megavolt, do you have a low thermal short for when doing zero calibration?

I have a special shorting from Keithley. I bought it specifically so that I had something to answer this question ))

The device stood and carried out automatic measurements for several days. With installed short Keithley. Then I interrupted the measurement. Updated firmware and continued measurements. After that, a clear step appeared on the chart before and after the update. (I will add a graph in the evening)

[MegaVolt]

Left - 5 day test
Right - 3 day test after update.

[Kleinstein]

Updating the firmware may imply running an ACAL. This alone could change the offset a little.

[MegaVolt]

Updating the firmware may imply running an ACAL. This alone could change the offset a little.

For two years I played with the device and started ACAL. Mixing was kept at 300-400nV very stable.

I assume that it is possible that ACAL can start after updating the firmware without turning off the power, but it doesn’t work as intended. It is not very clear why repeated ACAL does not return anything

[E-Design]

Updating the firmware may imply running an ACAL. This alone could change the offset a little.

For two years I played with the device and started ACAL. Mixing was kept at 300-400nV very stable.

I assume that it is possible that ACAL can start after updating the firmware without turning off the power, but it doesn’t work as intended. It is not very clear why repeated ACAL does not return anything

Updating the firmware requires a reboot which isnt as thermally upsetting as a power cycle but it still might make a small shift. I would expect though, the zero to eventually return to its previous value after some time.

An ACAL however, will rebuild the zero measurement and now becomes dependent on how good of short and thermally stable you can make at the terminals.. It will in general, end up being slightly different.

For your thermal short, check the orientation of it. It is not thermally symmetric. Rotate it and let unit sit for > 1 hour, you will see a shift. It is designed for stable HI-LO but as you can see there is also a SHI-SLO and the two connect. Anyways, the orientation is another variable. Also, you didnt say, are there air currents or other instrument nearby creating less stable environment. I couldnt see your picture because its only the graph not the instrument.

[MegaVolt]

I carefully checked the captured data and found this jump before flashing. I apologize for the uproar. I was wrong.
Unfortunately, I cannot find an explanation for this phenomenon other than a decrease in temperature by a couple of degrees.
But this phenomenon is definitely not related to firmware.
The graph shows data with NPLC = 5 and averaging filter = 12

[eplpwr]

Two days ago I filed a support case with Tek regarding the temperature in Celsius being shown as kilo-degrees.

Today I received a FW version 1.7.3c and can report that my specific problem is fixed. From what Tek/Keithley wrote, is seems like this version is very close to being published on their site. 



Unfortunately, I didn't get any release notes (PDF file), just an .upd file that flashed without problems, so I don't know what other fixes are in there.

Best regards,

eplpwr

[MegaVolt]

Two days ago I filed a support case with Tek regarding the temperature in Celsius being shown as kilo-degrees.

Tell me through which communication channel did you get such a quick response?

Today I received a FW version 1.7.3c and can report that my specific problem is fixed. From what Tek/Keithley wrote, is seems like this version is very close to being published on their site. 

Can you share this firmware? Or is she under NDA

[eplpwr]

Tell me through which communication channel did you get such a quick response?

I used the support form on tek.com.

[MegaVolt]

The firmware actually appeared on the site
https://uk.tek.com/digital-multimeter/dmm7510-software/model-dmm7510-firmware-revision-173-and-release-notes

But I can't download it because: "In compliance with U.S. Government regulation, Tektronix is required to review all software download activity. This process may take up to one U.S. business day and you will be notified when the process is complete. We apologize for any inconvenience." 

I'll wait for the day )))

[MegaVolt]

I cannot download either the new or the old update. Did anyone manage to download the new update? Can he put it somewhere?

[coromonadalix]

Their website works awfully,  they messed up my registration, lots of lags ?? in my case.  To force people to register   pfffffff

heres your file   v 1.73

https://gofile.io/d/KhSSup

around 7.2 megs

Release note pdf  added

[coromonadalix]

Version 1.7.3 provides fixes and enhancements.
CRITICAL FIXES

Reference number: NS-1908
Symptom: Changing an annunciator setting (such as auto zero or filter enable) on the
Settings or Calculations screen is not reflected in the Home screen
annunciators.
Resolution: This issue has been corrected.

Reference number: NS-1909
Symptom: Temperature readings are shown as k (for kilo) degrees Celsius,
Fahrenheit, or Kelvin instead of degrees Celsius, Fahrenheit or Kelvin.
Resolution: This issue has been corrected.

Reference number: NS-1927
Symptom: The LXI identification web page shows the incorrect LXI version and web
page links.
Resolution: This issue has been corrected.


ENHANCEMENTS

Category Remote commands

Reference number: NS-1931: Added a TLS (transport layer security) option when using the
tspnet.connect() command.
connectionID = tspnet.connect(ipAddress, portNumber,
 initString, useTLS)
ipAddress: A string that indicates the IP address or host name to
connect to.
portNumber: Default 5025.
initString: Sends a string to ipAddress.
useTLS: 0 or 1;
0: Do not use TLS with the connection (default)
1: Use TLS with the connection.
When useTLS is set to 1, the instrument negotiates the security protocol
when connecting to the host or IP address that is used. This security
protocol is used when using tspnet.write() to send data or
tspnet.read() to receive data.

Version 1.7.3 Release DMM7510 7½ Digit Graphical Multimeter Version 1.7.3 Firmware Release Notes
DMM7510-FRP-V1.7.3 June 2020 Page 5 of 49
The following is an example of how to use a host name with the TLS
option:
connectionID = tspnet.connect(“hostname.domain.com”,
 443, “”, 1)

Category Remote commands

Reference number: NS-1960: The localnode.gettimewithfractional() TSP
command is available to retrieve the number of seconds elapsed since
January 1,

[dmitry.bond]

Found that DMM7510 may have different probe port types. Either nice shrouded or unshrouded with thicker conductors (my guess).   
Is it an option or Tek changed the design? What is the latest?

[MegaVolt]

Photo of my device. It's 2018.
Where did the second photo come from?

[E-Design]

Photo of my device. It's 2018.
Where did the second photo come from?

Megavolt, the newer style is a cost reduction change but the contacts have the same performance. It is a product change that happened a few years ago to remove some unnecessary cost.

[MegaVolt]

New KickStart 2.4.0 released.

https://uk.tek.com/software/kickstart/2-4-0

[MegaVolt]

E-Design in the topic for 6500 you gave typical data for linearity 6500. Is it possible to see this data for 7510 as well?

[MegaVolt]

New Firmware Revision 1.7.5 released.

https://www.tek.com/sitewide-content/software/m/o/d/model-dmm7510-firmware-revision-175-and-release-notes

[E-Design]

Per Request,

Typical linearity performance of DMM7510. NOTE: data for one sided only. Other side is mostly symmetrical.

[jjoonathan]

Speaking of linearity, what's the cal-lab technique for achieving it? I've heard that the 3458A has a special unique autocal self-linearization process that makes it 50x more linear than, say, the DMM7510, but what's the process? A really good Kelvin Varley divider or something?

[TiN]

Per Request,

Typical linearity performance of DMM7510. NOTE: data for one sided only. Other side is mostly symmetrical.

Excellent dataset, thank you. But it brings some more questions, as shape is bit strange if its indeed symmetrical.
I suspect that might be a linear fitting artifact, or there is really -0.2ppm pole at near 0V?
Also if there are datasets on other DCV ranges, that's be interesting. Some other meters are not as good for non-base 10(20V) range and INL for those rarely tested by people.

I also join to a question if you can share bit more about methodology?

[Kleinstein]

The INL curve looks like relative to a linear fit for only the positive readings. Separate curves make absolute sense if something like Fluke 5700 calibrator is used to set the test points, as the fluke switches sign by relays and may show a small jump at zero.
From the data it looks like there is an additional meter used.

With a linear fit to only the shown data, the curve makes absolute sense.  It looks like a combination of U² and U³ parts and some small more local wiggles from something like idle tones. A fit to the whole range including the negative side would better decide between U² and U³ parts. The absolute error would get larger, as the curve needs to join at zero. So the error bound do not directly apply.
 U³ and U² parts can arise from resistor self heating and the FET switch resistance, so they are the normal errors to expect.
Especially the U³ part from resistor self heating may vary between units, as it is about proportional to the relative TC.

The curve still looks good.

[MegaVolt]

A little about the good ))
The device has a very low noise level. With inputs shorted in the 0.1V range and NPLC = 1, 42nV RMS can be obtained.
But if you add together several buffers with measurements and average them, you can reduce the noise level by the root of N times !!!

For example, here is the result of averaging 100 buffers.
RMS noise = 4nV !!!!!

P.S. such processing of measurements helps to reveal some measurement artifacts. I'll talk about this a little later.

[Kleinstein]

I know about the usual reduction of noise level from averaging, but this only work so easy if the readings are independent, and this can be a problem with the 7510 for 2 reasons.
One is the ADC part, likely from the auto zero mode, there seem to be some correlation between the readings, e.g. from averaging the zero readings. This is one of the problems discussed in this thread for th noise in the 10 V range. There averaging does not follow simple theory. For the 100 mV range the ADC may not be that relevant, at least not the noise level for 1 PLC.

The second point is the configuration of the input stage. From the photos and analogy with other keithley meters the input section is expected to use low noise JFETs and an AZ OP to compensate drift. This would be very low noise at high frequency, but only moderately good at longer integration or averaging multiple readings in a row. To reach such a low noise level it would need more like classical auto zero, like in most HP meters with switching before the amplifier. So the AZ OP may be just there for the non AZ mode    .