Kelvin (4-Wire) Milliohm Meter: Version 1.3 Enclosure

This post documents an enclosure for the milliohm meter described here and is a tale of how the mechanical bits are often as difficult to get right as the electronics.  The meter parts have been stored away, and thus it was not really available due to the lack of an enclosure.  Today I finally got around to putting it all together.

Here it is all wired up but outside of the enclosure:

I am not that pleased with the wiring - too easy to bump loose and not that tidy - but easy removal seemed desirable and it could be hot glued or otherwise made more robust.  I have a new crimp tool on order along with different types of connectors so I can make a better job of it next time.

Shabaz posted his build based on Version 1.0 and made a comparison to a Keithley DMM 6500 here.  My new build is in a larger enclosure with banana sockets on the front and also incorporates a power on LED and out of range LED.  The enclosure, rocker switches, and panel mounted LEDs  were all ordered at the same time.  Lots of room inside. Unfortunately the enclosure is not quite tall enough and there is not room for labels on the front.  Doh!  Smaller toggle switches and new panel LEDs to match are on order.

It is useable again though.  Above it is measuring a 1 ohm 0.5% resistor.  The enclosure came with aluminum end plates but I thought I would try PLA on the 3D printer and that came out quite well I thought.  It took 3 attempts...

• First trial - All of the holes and penetrations were too small by about a millimeter or two.  I "fixed" that with a file so everything fit but my filing was not that even so I modified the model and printed it again.
• Second trial - Things fit but I didn't like the way it looked :-) and tweaked it a bit.  The volt meter also was a bit wobbly because of the plate thickness so a thicker lip was added around it.
• Third time a charm - That is what you see above.

One of these days would like to make it auto-ranging.  Until then, this will do fine....

As I reflect back on this it seems that a element14 user generated brochure with tips on creating robust wiring and enclosures or just good builds in general would be nice...

Past Posts on this Project

Milliohm Meter: Version 1.3 First Test

Milliohm Meter: Version 1.0 Shabaz Build

Milliohm Meter: Version 1.0

Lots of other posts behind these...