Fluke 884X-SHORT youtube rant.

[Macbeth]

Just found this. Thought you metrology guys would find it amusing!



Apart from the obvious fail it's worth watching through his investigation. Warning. Do not be drinking coffee over the keyboard. I lost it when the microscope and calipers came out... 

[saturnin]

 

The video is more than one year old - I only wonder whether he still believes Fluke (=masters in metrology field) made a bad design or he has finally found out what was wrong 

[Macbeth]

I actually thought this was some kind of April 1st thing as it was uploaded early April 2015. But he persists a few days later not realising what he did wrong...



There's quite a treasure trove of EEVBlog-esque videos on his IEBlog channel, all ending with the familiar "if you liked this video please give it a thumbs up!" 

[Kleinstein]

Whether you need have the arrow up/down or sideways depends on the layout of the terminals. This is a 4 wire short, but only good if the thin link is between the current driving and the voltage sensing termnal, not when mixing them. So there is a 50% chance to get it the wrong way around.

There are special versions that allow to rotate them at will, more like a "perfect" star point. But this more difficult  / expensive and not needed for a DMM.

[Macbeth]

I would like to know why both Keithley and Fluke chose to use a very fine trace of copper between the sense and input terminals on their 4 wire shorting blocks instead of  the same width tracks all around. Why not an X or a square? Also Keithley (8610/8620) have theirs right in the centre (like a H) while Fluke have their tiny trace (like a U)?

Is the 12.5mOhm trace actually acting like the equivalent resistance of using normal Kelvin leads all shorted at the tip perhaps?

[Kleinstein]

The thin trace makes sure that the contact between the current and voltage leads is really point like. Though its only important to have a point like contact, not that the line itself is thin. Just a full copper plane would not be a good zero ohms resistor.

There is also a good thing in having a relatively large resistance when used the wrong way around: the 12 mOhms value is obviously bad, so one should note the wrong reading and turn the short. So if there is something to complain, it's more like that the 12 mOhms are not enough to make it obvious to everyone.