I am an engineer old school.
Oh well in
that case: I gathered some info from the design engineers. We're really quite happy to share details, but it helps us if you're specific in what you want to know and why you want to know it. I think I addressed all the questions below:
To know when the relay will click, and when not.
The relay positions aren't documented right now so I just found these by trial and error. I'll see about making a cohesive table for this later, I know reading it in text form is complicated. If you go
into or
out of the following functions/ranges, you will hear a relay actuate. These are only for Voltage, current, and ohms. The other functions reuse these relays.
For the DMM6500: Relays are used for the AC I/V functions, ACV 10V and higher, DCV 1000V, 10 Ohms and lower (both 2W and 4W), 100mA range and 1A and higher ranges both ACI and DCI. The DC/ACI >=1A relay is the same as the <1000DCV relay, so switching between those will not have a relay click. Digitize functions use the same relays as their DC counterparts.
For the DMM7510, assume it's the same as the DMM6500, but with these differences: No relay for low ohms but instead has a relay for 10MOhm and above. DCV has no 1000V relay. DigiV has a relay for 10V and below (>10V shares the relay with DCV). I don't think I missed any...
What is the input bandwidth for DCV.
From a purely hardware perspective up to but not including the ADC: up to hundreds of kHz to support the DCV digitizer function for 10V and less ranges. 100V and 1000V ranges a lot less than that due to internal 10Meg divider. Generally similar to digitzer specs.
Is it possible to somehow find out the exact values of current shunts. The device itself must know them?
The Nominal values are copied here from the specifications: 10 μA-10 kΩ; 100 μA-1 kΩ; 1 mA-100 Ω; 10 mA-10 Ω; 100 mA-1 Ω; 1 A-100 mΩ; 3 A-100 mΩ; 10 A-5 mΩ. These have a 1% tolerance. The exact values are never measurable by the DMM or otherwise because of the path resistances and connections inherent to the DMM (unless you open the box and cut the resistors out).
How are the processors, trigger connected inside ...
And any other information on the device. Scheme. Block diagram Sketches.
The processors/trigger/measurement relationship is too complicated to document here and changes depending on the specifics of how you're measuring. Is there some case you had in mind? We want to try and answer your question, but we could make hundreds of different block diagrams about the box.
the actual data rate / time spacing
Do you mean the flow of data out of the box? Or the spacing of measurements? Typical reading rates out of the box for the best case scenarios are given in the datasheet, they'll go down from there. Spacing of measurements are controlled by things like autozero, multiphase measurements (so like 4-wire ohms, DCV ratio, things where one measurement really takes more than one measurement), line sync, aperture, autoranging, autodelay, etc. I don't think it's practical or possible to list all the possible combinations and the spacing for each function.
actual aperture and measurement sequence in the Ohms modes
The aperture for ohms modes is settable like in any other function, unless you meant something else? The measurement sequence is different depending on what range you have selected (the 10M and 100M range use a ratiometric method, described starting on page 204/5-59 of the manual) and certain measure settings like offset compensation and open lead detection add extra phases before the measurements take place. Depending on your particular settings, the measurement sequence gets up to 7 phases long for 4-wire ohms.
Also for the digital filtering used in the meter, it would be nice to know about the exact filter function, as this effects noise estimates from the readings. With filtering use the simple std. deviation values calculated have to be taken with a grain of salt - as the raw data may be correlated.
"Filter" Filtering is applied by the digital process after calibration is applied to the readings. There are two different types of filtering that are detailed on page 198/5-53 of the manual, plus Hybrid filtering which is in the 1.0.01f firmware release notes or I wrote about it earlier in this thread (
https://www.eevblog.com/forum/testgear/new-keithley-dmm6500/msg1768589/#msg1768589). All this "post-processing" follows an order of operations on page 215/5-70, I attached an image of it too (which is actually a bit misleading, going to the display and the buffer actually happen simultaneously, I put a bug report in for that).
Not knowing such details might lead to problems like not always waiting long enough for settling. This could lead to problems like the odd out-layers once every 160 readings seen in some cases - though in this case more like a problem for the DMM internal software.
You can definitely configure the box so that the DMM won't return settled measurements. The power up default enables Autodelay which ensures settling in most cases. The times added by autodelay are given starting on page 189/5-44 of the manual. If you have an atypical setup, like really long cables or circuits, you may need to add manual delays.