The 3706A is another instrument with dry circuit measurement, I think that's the only 3 we offer with dedicated dry circuit modes. The DMM6500/DAQ6510 don't have the hardware required to do dry circuit testing, so that's a feature that can't be added in later (without a new model number). It was looked at, but the team decided the cost for adding that one feature would've been too great.As a compromise, is there anything which would prevent me from doing the following hack as a TSP script?
- Connect an external high stability 2 ohm in parallel with DUT (open would be 20mV on the 1 and 10 ohm ranges?)
- Measure the 2 ohm alone, store the value
- Deduce the DUT and display only the calculated value
One caveat is that pecision would become exponentially worse above 2 ohms, but that's all I need anyway for small signal relay contacts.
@nictinkers, thank you for the feedback! I'm sorry you don't care for a lot of the design, but really, we do take all the feedback we can get to heart.
Not exactly what you really want I think, which would require 2 full ADCs, but the DMM6500 can measure power with the voltage ratio function like the other DMMs in its class.
Not exactly what you really want I think, which would require 2 full ADCs, but the DMM6500 can measure power with the voltage ratio function like the other DMMs in its class.
That's an interesting approach. I like that using an external shunt doesn't age the relays switching from voltage to current. Is there a way to fill a buffer of full ratio measurements at a high speed with a fixed sample frequency? (That is, like Digitise Voltage, but for full ratio.) Even if you couldn't hit 1 megasample/sec I'd assume you could get fast enough to get a low-distortion measurement for 50/60Hz signals. Then it would depend on whether the scripting language is then powerful enough to calculate AC power parameters from the buffer.
The 3706A is another instrument with dry circuit measurement, I think that's the only 3 we offer with dedicated dry circuit modes. The DMM6500/DAQ6510 don't have the hardware required to do dry circuit testing, so that's a feature that can't be added in later (without a new model number). It was looked at, but the team decided the cost for adding that one feature would've been too great.Thank you for your answer.
As a compromise, is there anything which would prevent me from doing the following hack as a TSP script?
- Connect an external high stability 2 ohm in parallel with DUT (open would be 20mV on the 1 and 10 ohm ranges?)
- Measure the 2 ohm alone, store the value
- Deduce the DUT and display only the calculated value
One caveat is that pecision would become exponentially worse above 2 ohms, but that's all I need anyway for small signal relay contacts.
Hi Brad, following up on this ratio topic, is there anyway to display the sense/Vs voltage onto the screen as well alongside the Vinput. Like the keysight is able in the video (2:09)
https://youtu.be/Y6xnLkiUMn8?t=129
thanks!
Yeah, that's real easy.
Getting this DMM out of US customs is incredibly frustrating, is this paranoid crap a new thing?
It doesn't have "dry circuit" voltage limits on the low ohm ranges, only the 7510 and the 2010 seem to have this option?
I was wondering if it could be added later in firmware, or in scripting, or whether it's an actual hardware limitation on the 6500.The 3706A is another instrument with dry circuit measurement, I think that's the only 3 we offer with dedicated dry circuit modes. The DMM6500/DAQ6510 don't have the hardware required to do dry circuit testing, so that's a feature that can't be added in later (without a new model number). It was looked at, but the team decided the cost for adding that one feature would've been too great.
@nictinkers, thank you for the feedback! I'm sorry you don't care for a lot of the design, but really, we do take all the feedback we can get to heart.Also that the instrument doesn't measure voltage and current simultaneously. It would have been really nice to be able to measure power, power factor, VA, VAR, even at some much lower resolution and accuracy than the main ADC.Not exactly what you really want I think, which would require 2 full ADCs, but the DMM6500 can measure power with the voltage ratio function like the other DMMs in its class. One of our engineers wrote a small script to simplify the process a bit, the script and the full description are here: https://forum.tek.com/viewtopic.php?f=617&t=141154,
here's a video he's been putting together for it too:
https://youtu.be/oWTTrA20M0w
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The lowest resistance range is very noisy as expected, getting usable values that low requires slow integration and filtering. Averaging reaches the point of diminishing returns around 5 NPLC with 100x repeat filter. A hundred readings took a little over an hour. Doing 15 NLPC with 100x filter took 3 hours and provided very similar numbers. It's either the limit of the instrument or the limit of my crude methodology.
The limited effect of more filtering / longer averaging is a kind of weak point with quite some Keithley meters.
Getting this DMM out of US customs is incredibly frustrating, is this paranoid crap a new thing?
thank you very much for the script, however there seem to be an issue with the readingbuffer, that every time the script is ran it seems to change the reading buffer to fill mode "once", even when i manually change the fill mode back to continuous on the dmm, so the script eventually stops itself. Is there anyway to change the fill mode to continuous in the script?. I noticed this aswell on the power measurement script aswell
Thanks!!
readingBuffer.fillmode = buffer.FILL_CONTINUOUS
powerBuffer.fillmode = buffer.FILL_CONTINUOUS
The lowest resistance range is very noisy as expected, getting usable values that low requires slow integration and filtering. Averaging reaches the point of diminishing returns around 5 NPLC with 100x repeat filter. A hundred readings took a little over an hour. Doing 15 NLPC with 100x filter took 3 hours and provided very similar numbers. It's either the limit of the instrument or the limit of my crude methodology.
The interface is a lot of fun to use, there are still a few things that I hope will be adressed in a firmware update. Not a big deal, the yellow cursor have no reason to exist on the 6500 since there's no knob to control it (it seems to have been written more for the smus and the 7510) unless I didn't figure out how to move it around. It makes the behaviour of the enter key a bit random, it's whatever default was selected on the page.
The swipe to change pages can be risky to operate, I sometimes press one of the functions by mistake, which wipe out the currently running acquisition. I would love to cycle the pages with the home key or something, maybe an option to remove the function page completely since there's already a dedicated function button to popup that menu. Maybe a toggle to prevent interrupting the measurement? A dialog yes/no for anything which would clear the buffer? Something like that. When running a trigger and count other than plain continuous, the content of the buffer is probably important.
display.delete(display.SCREEN_FUNCTIONS_SWIPE)
to bring it back:display.create(display.SCREEN_HOME, display.OBJ_SWIPE, display.SCREEN_FUNCTIONS_SWIPE)
You could add these to autoexec.tsp to have the swipe removed on start up.display.SCREEN_FUNCTIONS_SWIPE
display.SCREEN_SETTINGS_SWIPE
display.SCREEN_SECONDARY_SWIPE
display.SCREEN_GRAPH_SWIPE
display.SCREEN_STATS_SWIPE
The very low resistance means measuring very low voltage and there thermal EMF effects at the "resistor" can also limit the accuracy. It might help to cover the resistor to protect it from air drafts. Thermal EMF combined with temperature fluctuations is one of the limiting factors for long time averaging. This is inside the meter and also at the DUT. For the copper resistor this could also be just a fluctuation of the resistance due to temperature changes.
I wish they enabled a 1000x repeat filter for a 1 NLPC reading, which would probably yield one least significant digit in the 1 ohm range. All other ranges are ultra stable and don't really need this. That 1 ohm range is already crazy impressive but it can still be improved in software even more.
.....
The lowest resistance range is very noisy as expected, getting usable values that low requires slow integration and filtering. Averaging reaches the point of diminishing returns around 5 NPLC with 100x repeat filter. A hundred readings took a little over an hour. Doing 15 NLPC with 100x filter took 3 hours and provided very similar numbers. It's either the limit of the instrument or the limit of my crude methodology.
The limited effect of more filtering / longer averaging is a kind of weak point with quite some Keithley meters. If think they should work on this, as it is very likely fixable in software and it effects not just the 6500. This seems to be an old problem (AFAIR I saw the odd low frequency noise already on an old 196 or 199) so I would no expect a fast solution. My hope would be more on finally finding out when developing a new 8 digit meter.
The DAQ6500 is more like a meter for fast measurements and only specified for 6 digits. So the relatively poor noise with 10-60 seconds averaging is not that significant for this type of meter. It's more the higher grade 7510 where this really hurts. The good thing is, chances are it gets better once averaging is much longer (e.g. 5 minutes).
The very low resistance means measuring very low voltage and there thermal EMF effects at the "resistor" can also limit the accuracy. It might help to cover the resistor to protect it from air drafts. Thermal EMF combined with temperature fluctuations is one of the limiting factors for long time averaging. This is inside the meter and also at the DUT. For the copper resistor this could also be just a fluctuation of the resistance due to temperature changes.
The user manual has the following information: At these rates (lowest noise region in graph), DMM6500 will make corrections for its own internal drift and...
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