In any field there are instruments, and then there are the little additions that make the intruments do those extra little functions and therefore add value to them. This section is dedicated to those little additions that no-one else will have, because you had to build them yourself!
But before we continue, there is one thing I have found absolutely vital to making life easier....
Daft statement? Not really. Although the 4mm Shrouded Banana Plug is making more and more inroads into the mains and HV test market, there are still many instruments that do not use this system. Ok, it's not perfect, although it is better than most - and it's reasonably cross-compatible with older instruments.
What does become important is to create a test lead system whereby fewer leads need to be carried to site to accomplish the task at hand. How convenient it becomes when the test leads, which were plugged into e.g. the multimeter, are simply transfered to the voltage recorder.
My personal favourite is the 4mm 'shrouded' range for anything that can bite (50V and up) or has the ability to move plenty electrons in an incredibly short space of time (or damaged when asked to move too many electrons in one go). Effectively 4mm means 'voltage'.
For passive circuits, such as current clamps, I like using BNC connectors. These are usually found on low voltage instruments such as oscilloscopes so having a connector that fits directly in makes for simple operation. Yes, there are a few 4mm-BNC convertors in the bag.
If you are going to follow suite then please use shrouded types to remove the potential danger of touching high voltage circuits with the BNC casings. Also use a good quality, high grade coax that is both flexible and has a decent outer sheath so as to minimise any potential flash-over at the voltages you're likely to work at.
For potentially dangerous areas there are a few short pieces of double shielded coax lengths in the bag. These had to be home made and were created from lengths of RG58 housed inside the sheaths of RG59.
Finally, there is one thing that can drive me nuts! All equipment should be fitted with what must now be the most common power connector found nowadays - the IEC320 (as found on almost all personal computers and peripherals). What I really think is so cool about this connector is if I should forget the power lead for an instrument, then I simply have to whip into the nearest store carrying anything close to electrical bits and pieces and I will be able to buy a replacement. Also, if having to quickly cross the pond to another country, I can again simply ask for a computer power cable and the equipement is up and running.
Another heading for this is "making double adapters". It may appear as a waste of space but, believe me, many calls have been taken where an engineer has been stumped into not being able to do a measurement by not having a facility to split the test points.
There are usually two scenarios that call for such 'double adapters'. The first is a single test point needing to be connected to two inputs such as delta connections. The next is a similar requirement but where a single test point needs to be fed to two completely separate instruments (such as a current clamp into a recorder and an oscilloscope).
One last requirement (one that must be approached with caution) is wanting to power an instrument from the voltage under test. Being able to split the test point allows for far safer testing.
And finally; I cannot stress enough how vital it is, should you be building your own testing aids, to build with safety in mind and thus do a proper job from the outset. I have seen the most hideous "test bits", obviously built in a hurry with that all familiar "I'll get round to making a proper job of it later" approach - but it never gets there!