quick follow-up question, I noticed Kithley has also a DMM7500, which is 7.5 digits.
Is the 7500 identical to the DMM6500 (except higher resolution) ?
Also, looks like they have a DMM7510. How does that compare ?
I have not seen a DMM7500, but have both the DMM7510 and DMM6500. They are not the same, even though the screens looks similar and they have about the same functionality.
Some difference:
The DMM7510 has a rotary encoder, this makes it possible to use it without the touchscreen (If it ever fails).
The DMM7510 has light in its buttons.
The DMM6500 has a slot for a switch module, i.e. it can be used to monitor multiple channels.
The DMM6500 has some special support for apps (Some can be downloaded from Keithley) Note: They can both run scripts.
On the DMM6500 the amp fuse can be changed from the front.
My DMM7510 has a considerable more noisy fan than my DMM6500, for this reason I mostly use the DMM6500.
The DMM6500 is a slightly never design and if you don't need the extra digit I believe it is a much better package.