Oh, just to add, I now  have a multitude of length measuring devices: digital Vernier, several steel/aluminum rulers/tapes and wheel pacer....maybe I'll top it off with an ultrasonic or laser ranger one day. In fact every tape measure bought for 'in the house use' eventually migrates to the shed

My first measurement tool would have been the wooden ruler I had to buy at junior school. It lasted a long time, got nicely soaked in ink and the edge chipped away. The trouble was as you strived for better accuracy the marks were a few mm away from the back due to the thickness of the ruler. However it finally got replaced with a more accurate and 'shatterproof' green ruler (which was actually shattered I recall). I don't know what happened to the old wooden one - maybe it was used to light a fire or splint a broken leg ?

My first measurement tool was my dad's multimeter. It was my dad's way of sharing his passion. I used it for countless electronic kit projects growing up. Before that I used to use it, along with his oscilloscope as part of my pretend airplane cockpit dashboard. That was the start of the path to a 15 year career in electronics. That multimeter is still in my dad's toolbox for when I need to help my mom with jobs around her flat.

My first measurement/test tool was my finger. Is it hot, are those CMOS inputs floating, does changing the capacitance tune this better. I still have it, although I've replaced the thermometer mode with a pico TC08 USB now and I've added higher precision tools over the years

My first tool wasn't really mine at the time, it was my dad's. I had a transforming robot / jet fighter toy with blaster sounds and flashing lights. And it wasn't blasting or flashing. The batteries might have been dead for all I knew. I described this over the phone to my dad. "Why don't you use my multimeter to fix it?"

Considering I had never even turned a screwdriver, this was a big deal. I found the bulky multimeter he described, and it was awesome. It had a needle that would zoom into position, then bounce back and forth a little bit. Suddenly I was able to see electricity. I wasn't stupid enough to probe a wall socket, but the thought absolutely did cross my eight-year-old mind. Considering I didn't know there's a difference between AC and DC, or just how important voltage can be...

I don't have the meter anymore, at least I think. I still haven't gone back through all his tools, accumulated over the years. It's been replaced in my own collection with a couple of digital models. They're technically superior in every way, but I still have a soft spot for analog needles flicking across a dial like a dowsing rod.

Like many of us, the first specific to electronics was a dmm and the cheapest available, served its purpose but at least a dozen since then...

My exposer to voltage & resistance  measurement was 40 years back, when my 8th grade teacher taught us assemble a two band transistor packet radio ( mw & sw).consiquently I became service engineer for entire class using anlog multimeter.now when I maintain  satilite based equipment or proffestional cameras using latest instruments bz the base was very strong.

Sweet memories and thankfull to  my teacher Mr. Somasundaram sir.

Colour me impressed!  There’s something about building your own test tools that is satisfying.  Mine were all in software though, the best ones back in the early days of client-server and component-based computing.  I think that’s a way load easier than what you managed to build there.

When I first started developing digital systems for nuclear research (Carbon 14 dating, flame photometry, mass spectrometry, Tritium dating etc.) around 1972 I had a logic probe, logic pulser and an analogue scope, not much to test and diagnose fairly complex systems. I designed a built a test unit which had a tracking power supply (to automatically match unit under test UUT), and also drove a variety of inputs and outputs - no uP involved, all discrete logic - from memory it had 8 digital outputs both toggle and momentary, 16 channel digital inputs, latchable to monitor and capture all IC pins (had a panel so the actual pinouts could be drawn on the unit to provide immediate identification of pin functions while monitoring). Variable frequency output with variable mark to space, single pulse output with variable period, 16 bit serial data capture to monitor serial interfaces, and a race detector to measure circuit race conditions down to nS. It also had a programmable period on/off relay to allow power supply cycling of UUT to monitor reboot reliability (some circuits failed once every few days). It fairly soon became redundant as I was allowed to purchase more sophisticated commercial units, digital scopes and logic analysers, but it got me started, and on occasion dug me out of some strange design holes. Black anodised panel with lots of red LEDs, rack mounted about 4 units high it looked pretty sexy too!

I didn't manage to save that unit, but I do still have the prototyping platform I developed around the same time - 50 years old!

The first measurement tool I remember well was vernier caliper. I was studying at University, got impressed with its precision and decided to read more about the visual effect it is using - Moire effect, just for fun. Shortly after I applied for a job and they asked me to write a paper on any physics effect applied to any common item. So I did - about caliper an Moire effect. And I got the job!