Salvaging a Multi-Meter
Posted on: 9/28/2013
So today's adventure involves a multimeter I seen laying outside of my friend's house. According to him it has seen the rain more than once, and he was convinced it was dead. When I first turned it on, it did do some funky shit. Numbers were jumping all over the place, the leads were all rotted up, and it looked like the 9 Volt battery was leaking out of the side. Still, I was convinced I might be able to do something with it, so I took it home.
This is one of those cheap meters you can pick up for under 20 bucks. Most would ask: What's the point in fixing it? Why not just buy another one? I can only answer these questions with one response: Because I can! First thing is first, I tore it open to find that the battery was indeed rusted up and leaking, and the 9V battery connector was missing a chunk. I'm not fond of batteries myself, so I modded it to fit a power supply. Of course this modification defeats its mobility, but if I really wanted to I can just connect a 9V battery through this port later with a battery mod.

So now I needed a 9V DC power supply with at least 50mA. Unfortunately, this isn't very common to have just laying around the house. So looking at everything I have plugged in everywhere, I discovered that my phone ran on 9V. Score! Unfortunately I'm still gonna need this for my phone, and I could probably pick up an adapter from somewhere else. But I'm impatient and don't feel like driving 18 miles to Wal-Mart in the middle of a project. So now the cord has two ends, the one that runs to my phone, and the one that is gonna power my Multi-Meter (not at the same time of course).

If your memory serves you well, then you'll recall that I mentioned that the probes were shot. The leads were rusted up and snapped off with very little force, and the wires broke off the ends with little effort. Lucky for me the connectors to the multimeter were intact. So the question in my head was, what am I going to use for probes? After some brainstorming I saw a pile of fine tipped Sharpie markers that I almost never use. Perfect I thought to myself. With a little modification involving solder, two finishing nails, hot glue, and some wires I put together some "Sharpie Probes".

So now the most important question: Does it work? It sure does. I pulled out one of my modded wiimotes that is powered by USB and a voltage regulator circuit that breaks down 5V into 2.78V (which you can read more about here at the end), and poked around at it. All the voltages match up. The voltage regulator circuit in the wiimote is slightly off (supposed to be 2.78V), but this is most likely a slight issue with the circuit and not the multimeter itself. I went back and tested my white and blue wiimote and they both correctly read 2.78V, unfortunately I didn't snap any pictures. Outside of voltage regulator circuits, I also tested the 120VAC coming from the walls, and the 5V and 12V coming from my PC power supply. It all looks good! I'm not one who can throw anything away without first trying to fix it. Today I gained a multimeter with hilarious custom probes.